Doc: Update man pages for KEYCTL_RESTRICT_KEYRING

Created a new manual page for the new keyctl_restrict_keyring function and
added 'keyctl restrict_keyring' information for the keyctl command line
utility.

Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David Howells <dhowells@redhat.com>
3 files changed