Enforce module signatures if the kernel is locked down

Enforce module signatures if the kernel is locked down

If the kernel is locked down, require that all modules have valid
signatures that we can verify or that IMA can validate the file.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: "Lee, Chun-Yi" <jlee@suse.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
[bwh: Adjust context to apply after commit 2c8fd268f418
 "module: Do not access sig_enforce directly"]

Gbp-Pq: Topic features/all/lockdown
Gbp-Pq: Name 0004-Enforce-module-signatures-if-the-kernel-is-locked-do.patch