audit: avoid -Wempty-body warning

audit: avoid -Wempty-body warning

gcc warns about an empty statement when audit_remove_mark is defined to
nothing:

kernel/auditfilter.c: In function 'audit_data_to_entry':
kernel/auditfilter.c:609:51: error: suggest braces around empty body in an 'if' statement [-Werror=empty-body]
  609 |                 audit_remove_mark(entry->rule.exe); /* that's the template one */
      |                                                   ^

Change the macros to use the usual "do { } while (0)" instead, and change a
few more that were (void)0, for consistency.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Richard Guy Briggs <rgb@redhat.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>