eCryptfs: kerneldoc fixes for crypto.c and keystore.c

Andrew Morton wrote:
From: mhalcrow@us.ibm.com <mhalcrow@halcrow.austin.ibm.com>
> > +/**
> > + * decrypt_passphrase_encrypted_session_key - Decrypt the session key
> > + * with the given auth_tok.
> >   *
> >   * Returns Zero on success; non-zero error otherwise.
> >   */
>
> That comment purports to be a kerneldoc-style comment.  But
>
> - kerneldoc doesn't support multiple lines on the introductory line
>   which identifies the name of the function (alas).  So you'll need to
>   overflow 80 cols here.
>
> - the function args weren't documented
>
> But the return value is!  People regularly forget to do that.  And
> they frequently forget to document the locking prerequisites and the
> permissible calling contexts (process/might_sleep/hardirq, etc)
>
> (please check all ecryptfs kerneldoc for this stuff sometime)

This patch cleans up some of the existing comments and makes a couple
of line break tweaks. There is more work to do to bring eCryptfs into
full kerneldoc-compliance.

Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>