selinux: convert WARN_ONCE() to printk() in selinux_nlmsg_perm()

Convert WARN_ONCE() to printk() in selinux_nlmsg_perm().

After conversion from audit_log() in commit e173fb26, WARN_ONCE() was
deemed too alarmist, so switch it to printk().
Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
[PM: Changed to printk(WARNING) so we catch all of the different
 invalid netlink messages.  In Richard's defense, he brought this
 point up earlier, but I didn't understand his point at the time.]
Signed-off-by: Paul Moore <pmoore@redhat.com>

security/selinux/hooks.c

@@ -4727,9 +4727,10 @@ static int selinux_nlmsg_perm(struct sock *sk, struct sk_buff *skb)
 	err = selinux_nlmsg_lookup(sksec->sclass, nlh->nlmsg_type, &perm);
 	if (err) {
 		if (err == -EINVAL) {
-			WARN_ONCE(1, "selinux_nlmsg_perm: unrecognized netlink message:"
-				  " protocol=%hu nlmsg_type=%hu sclass=%hu\n",
-				  sk->sk_protocol, nlh->nlmsg_type, sksec->sclass);
+			printk(KERN_WARNING
+			       "SELinux: unrecognized netlink message:"
+			       " protocol=%hu nlmsg_type=%hu sclass=%hu\n",
+			       sk->sk_protocol, nlh->nlmsg_type, sksec->sclass);
 			if (!selinux_enforcing || security_get_allow_unknown())
 				err = 0;
 		}