[AUDIT] Fix signedness of 'serial' in various routines.

Attached is a patch that corrects a signed/unsigned warning. I also noticed
that we needlessly init serial to 0. That only needs to occur if the kernel
was compiled without the audit system.

-Steve Grubb

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

kernel/auditsc.c

@@ -992,7 +992,7 @@ void audit_inode(const char *name, const struct inode *inode)
 }
 
 void audit_get_stamp(struct audit_context *ctx,
-		     struct timespec *t, int *serial)
+		     struct timespec *t, unsigned int *serial)
 {
 	if (ctx) {
 		t->tv_sec  = ctx->ctime.tv_sec;