ecryptfs: crypto: Supply some missing param descriptions and demote abuses

Fixes the following W=1 kernel build warning(s):

 fs/ecryptfs/crypto.c:29: warning: expecting prototype for eCryptfs(). Prototype was for DECRYPT() instead
 fs/ecryptfs/crypto.c:360: warning: Function parameter or member 'crypt_stat' not described in 'lower_offset_for_page'
 fs/ecryptfs/crypto.c:360: warning: Function parameter or member 'page' not described in 'lower_offset_for_page'
 fs/ecryptfs/crypto.c:637: warning: Function parameter or member 'crypt_stat' not described in 'ecryptfs_compute_root_iv'
 fs/ecryptfs/crypto.c:1386: warning: Function parameter or member 'ecryptfs_dentry' not described in 'ecryptfs_read_metadata'
 fs/ecryptfs/crypto.c:1463: warning: Function parameter or member 'filename' not described in 'ecryptfs_encrypt_filename'
 fs/ecryptfs/crypto.c:1463: warning: Function parameter or member 'mount_crypt_stat' not described in 'ecryptfs_encrypt_filename'
 fs/ecryptfs/crypto.c:1897: warning: Function parameter or member 'encoded_name_size' not described in 'ecryptfs_encrypt_and_encode_filename'
 fs/ecryptfs/crypto.c:1897: warning: Function parameter or member 'mount_crypt_stat' not described in 'ecryptfs_encrypt_and_encode_filename'
 fs/ecryptfs/crypto.c:1897: warning: Function parameter or member 'name_size' not described in 'ecryptfs_encrypt_and_encode_filename'
 fs/ecryptfs/crypto.c:1897: warning: Excess function parameter 'crypt_stat' description in 'ecryptfs_encrypt_and_encode_filename'
 fs/ecryptfs/crypto.c:1897: warning: Excess function parameter 'length' description in 'ecryptfs_encrypt_and_encode_filename'
 fs/ecryptfs/crypto.c:2006: warning: Function parameter or member 'sb' not described in 'ecryptfs_decode_and_decrypt_filename'
 fs/ecryptfs/crypto.c:2006: warning: Excess function parameter 'ecryptfs_dir_dentry' description in 'ecryptfs_decode_and_decrypt_filename'

Cc: Tyler Hicks <code@tyhicks.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: "Michael A. Halcrow" <mahalcro@us.ibm.com>
Cc: "Michael C. Thompson" <mcthomps@us.ibm.com>
Cc: ecryptfs@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
[tyhicks: Fix typo in ecryptfs_encrypt_and_encode_filename() func docs]
Signed-off-by: Tyler Hicks <code@tyhicks.com>

fs/ecryptfs/crypto.c

@@ -1,5 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
-/**
+/*
  * eCryptfs: Linux filesystem encryption layer
  *
  * Copyright (C) 1997-2004 Erez Zadok
@@ -350,7 +350,7 @@ out:
 	return rc;
 }
 
-/**
+/*
  * lower_offset_for_page
  *
  * Convert an eCryptfs page index into a lower byte offset
@@ -627,9 +627,8 @@ void ecryptfs_set_default_sizes(struct ecryptfs_crypt_stat *crypt_stat)
 	}
 }
 
-/**
+/*
  * ecryptfs_compute_root_iv
- * @crypt_stats
  *
  * On error, sets the root IV to all 0's.
  */
@@ -1370,7 +1369,7 @@ int ecryptfs_read_and_validate_xattr_region(struct dentry *dentry,
 	return rc;
 }
 
-/**
+/*
  * ecryptfs_read_metadata
  *
  * Common entry point for reading file metadata. From here, we could
@@ -1448,7 +1447,7 @@ out:
 	return rc;
 }
 
-/**
+/*
  * ecryptfs_encrypt_filename - encrypt filename
  *
  * CBC-encrypts the filename. We do not want to encrypt the same
@@ -1876,10 +1875,11 @@ out:
 
 /**
  * ecryptfs_encrypt_and_encode_filename - converts a plaintext file name to cipher text
- * @crypt_stat: The crypt_stat struct associated with the file anem to encode
+ * @encoded_name: The encrypted name
+ * @encoded_name_size: Length of the encrypted name
+ * @mount_crypt_stat: The crypt_stat struct associated with the file name to encode
  * @name: The plaintext name
- * @length: The length of the plaintext
- * @encoded_name: The encypted name
+ * @name_size: The length of the plaintext name
  *
  * Encrypts and encodes a filename into something that constitutes a
  * valid filename for a filesystem, with printable characters.
@@ -1991,7 +1991,7 @@ static bool is_dot_dotdot(const char *name, size_t name_size)
  * ecryptfs_decode_and_decrypt_filename - converts the encoded cipher text name to decoded plaintext
  * @plaintext_name: The plaintext name
  * @plaintext_name_size: The plaintext name size
- * @ecryptfs_dir_dentry: eCryptfs directory dentry
+ * @sb: Ecryptfs's super_block
  * @name: The filename in cipher text
  * @name_size: The cipher text name size
  *