MAINTAINERS: update audit files

Add files maintaned by the audit subsystem.

Files from arch/*/*/*audit*.[ch] and arch/x86/include/asm/audit.h were not
added due to concern of the list not holding up over time.  There exist
already exceptions that caused the need for this specificity.

Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>