AUDIT: Fix definition of audit_log_start() if audit not enabled

audit_log_start() seems to take 3 arguments, but its defined to take 
only 2 when AUDIT is turned off.

security/selinux/avc.c:553:75: macro "audit_log_start" passed 3 arguments, but takes just 2

Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>