configfs: fix wrong name of struct in documentation

The name of the struct is configfs_bin_attribute instead of
configfs_attribute

Signed-off-by: Helen Koike <helen.koike@collabora.com>
Fixes: 03607ace80 ("configfs: implement binary attributes")
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/filesystems/configfs/configfs.txt

@@ -216,7 +216,7 @@ be called whenever userspace asks for a write(2) on the attribute.
 
 [struct configfs_bin_attribute]
 
-	struct configfs_attribute {
+	struct configfs_bin_attribute {
 		struct configfs_attribute	cb_attr;
 		void				*cb_private;
 		size_t				cb_max_size;