[PATCH] audit: fix broken class-based syscall audit

The sanity check in audit_match_class() is wrong.  We are able to audit
2048 syscalls but in audit_match_class() we were accidentally using
sizeof(_u32) instead of number of bits in _u32 when deciding how many
syscalls were valid.  On ia64 in particular we were hitting syscall
numbers over the (wrong) limit of 256.  Fixing the audit_match_class
check takes care of the problem.

Signed-off-by: Klaus Weidner <klaus@atsec.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>