LSM: fix documentation for the socket_post_create hook

This patch slightly fixes the documentation for the
socket_post_create hook. The documentation states that
i_security field is accessible through inode field of socket
structure (i.e., 'sock->inode->i_security'). There is no inode
field in the socket structure. The i_security field is accessible
through SOCK_INODE macro. The patch updates the documentation
to reflect this.
Signed-off-by: Denis Efremov <efremov@ispras.ru>
Acked-by: Kees Cook <keescook@chromium.org>
Acked-by: Casey Schaufler <casey@schaufler-ca.com>
Signed-off-by: James Morris <james.morris@microsoft.com>

include/linux/lsm_hooks.h

@@ -768,9 +768,9 @@
  *	socket structure, but rather, the socket security information is stored
  *	in the associated inode.  Typically, the inode alloc_security hook will
  *	allocate and and attach security information to
- *	sock->inode->i_security.  This hook may be used to update the
- *	sock->inode->i_security field with additional information that wasn't
- *	available when the inode was allocated.
+ *	SOCK_INODE(sock)->i_security.  This hook may be used to update the
+ *	SOCK_INODE(sock)->i_security field with additional information that
+ *	wasn't available when the inode was allocated.
  *	@sock contains the newly created socket structure.
  *	@family contains the requested protocol family.
  *	@type contains the requested communications type.