audit: force seccomp event logging to honor the audit_enabled flag

Previously we were emitting seccomp audit records regardless of the
audit_enabled setting, a deparature from the rest of audit.  This
patch makes seccomp auditing consistent with the rest of the audit
record generation code in that when audit_enabled=0 nothing is logged
by the audit subsystem.

The bulk of this patch is moving the CONFIG_AUDIT block ahead of the
CONFIG_AUDITSYSCALL block in include/linux/audit.h; the only real
code change was in the audit_seccomp() definition.

Signed-off-by: Tony Jones <tonyj@suse.de>
Signed-off-by: Paul Moore <pmoore@redhat.com>