docs: */index.rst: Add newer documents to their respective index.rst

A number of new docs were added, but they're currently not on
the index.rst from the session they're supposed to be, causing
Sphinx warnings.

Add them.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/crypto/index.rst

@@ -20,5 +20,6 @@ for cryptographic use cases, as well as programming examples.
    architecture
    devel-algos
    userspace-if
+   crypto_engine
    api
    api-samples

Documentation/driver-api/index.rst

@@ -18,6 +18,7 @@ available subsections can be seen below.
    infrastructure
    pm/index
    device-io
+   device_connection
    dma-buf
    device_link
    message-based

Documentation/process/index.rst

@@ -52,6 +52,7 @@ lack of a better place.
    adding-syscalls
    magic-number
    volatile-considered-harmful
+   clang-format
 
 .. only::  subproject and html
 

Documentation/security/index.rst

@@ -9,5 +9,7 @@ Security Documentation
    IMA-templates
    keys/index
    LSM
+   LSM-sctp
+   SELinux-sctp
    self-protection
    tpm/index