watchdog/softlockup: fix wrong output when watchdog_thresh < 3

When watchdog_thresh is below 3, sample_period will be less than 1 second.
So the following output will print when softlockup:

CPU#3 Utilization every 0s during lockup

Fix this by changing time unit from seconds to milliseconds.

Link: https://lkml.kernel.org/r/20250812074132.27810-1-yaozhenguo@jd.com
Signed-off-by: ZhenguoYao <yaozhenguo1@gmail.com>
Cc: Bitao Hu <yaoma@linux.alibaba.com>
Cc: Li Huafei <lihuafei1@huawei.com>
Cc: Max Kellermann <max.kellermann@ionos.com>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: ZhenguoYao1

kernel/watchdog.c

@@ -455,17 +455,17 @@ static void print_cpustat(void)
 {
 	int i, group;
 	u8 tail = __this_cpu_read(cpustat_tail);
-	u64 sample_period_second = sample_period;
+	u64 sample_period_msecond = sample_period;
 
-	do_div(sample_period_second, NSEC_PER_SEC);
+	do_div(sample_period_msecond, NSEC_PER_MSEC);
 
 	/*
 	 * Outputting the "watchdog" prefix on every line is redundant and not
 	 * concise, and the original alarm information is sufficient for
 	 * positioning in logs, hence here printk() is used instead of pr_crit().
 	 */
-	printk(KERN_CRIT "CPU#%d Utilization every %llus during lockup:\n",
-	       smp_processor_id(), sample_period_second);
+	printk(KERN_CRIT "CPU#%d Utilization every %llums during lockup:\n",
+	       smp_processor_id(), sample_period_msecond);
 
 	for (i = 0; i < NUM_SAMPLE_PERIODS; i++) {
 		group = (tail + i) % NUM_SAMPLE_PERIODS;