firewire: core: use guard macro to disable local IRQ

The core function provides an operation for userspace application to
retrieve current value of CYCLE_TIMER register with several types of
system time. In the operation, local interrupt is disables so that the
access of the register and ktime are done atomically.

This commit uses guard macro to disable/enable local interrupts.

Link: https://lore.kernel.org/r/20240805085408.251763-9-o-takashi@sakamocchi.jpSigned-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>

drivers/firewire/core-cdev.c

@@ -1263,29 +1263,27 @@ static int ioctl_get_cycle_timer2(struct client *client, union ioctl_arg *arg)
 	struct fw_card *card = client->device->card;
 	struct timespec64 ts = {0, 0};
 	u32 cycle_time = 0;
-	int ret = 0;
+	int ret;
 
-	local_irq_disable();
+	guard(irq)();
 
 	ret = fw_card_read_cycle_time(card, &cycle_time);
 	if (ret < 0)
-		goto end;
+		return ret;
 
 	switch (a->clk_id) {
 	case CLOCK_REALTIME:      ktime_get_real_ts64(&ts);	break;
 	case CLOCK_MONOTONIC:     ktime_get_ts64(&ts);		break;
 	case CLOCK_MONOTONIC_RAW: ktime_get_raw_ts64(&ts);	break;
 	default:
-		ret = -EINVAL;
+		return -EINVAL;
 	}
-end:
-	local_irq_enable();
 
 	a->tv_sec      = ts.tv_sec;
 	a->tv_nsec     = ts.tv_nsec;
 	a->cycle_timer = cycle_time;
 
-	return ret;
+	return 0;
 }
 
 static int ioctl_get_cycle_timer(struct client *client, union ioctl_arg *arg)