lockdown: ratelimit denial messages

User space can flood the log with lockdown denial messages:

[  662.555584] Lockdown: bash: debugfs access is restricted; see man kernel_lockdown.7
[  662.563237] Lockdown: bash: debugfs access is restricted; see man kernel_lockdown.7
[  662.571134] Lockdown: bash: debugfs access is restricted; see man kernel_lockdown.7
[  662.578668] Lockdown: bash: debugfs access is restricted; see man kernel_lockdown.7
[  662.586021] Lockdown: bash: debugfs access is restricted; see man kernel_lockdown.7
[  662.593398] Lockdown: bash: debugfs access is restricted; see man kernel_lockdown.7

Ratelimiting these shouldn't meaningfully degrade the quality of the
information logged.
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/lockdown/lockdown.c

@@ -63,7 +63,7 @@ static int lockdown_is_locked_down(enum lockdown_reason what)
 
 	if (kernel_locked_down >= what) {
 		if (lockdown_reasons[what])
-			pr_notice("Lockdown: %s: %s is restricted; see man kernel_lockdown.7\n",
+			pr_notice_ratelimited("Lockdown: %s: %s is restricted; see man kernel_lockdown.7\n",
 				  current->comm, lockdown_reasons[what]);
 		return -EPERM;
 	}