scsi: ufs: core: sysfs: Prevent div by zero

Prevent a division by 0 when monitoring is not enabled.

Fixes: 1d8613a23f3c ("scsi: ufs: core: Introduce HBA performance monitor sysfs nodes")
Cc: [e-mail]
Signed-off-by: Gwendal Grignou <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Reviewed-by: Can Guo <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/ufs/core/ufs-sysfs.c

···
 	struct ufs_hba *hba = dev_get_drvdata(dev);
 	struct ufs_hba_monitor *m = &hba->monitor;
 
+	if (!m->nr_req[READ])
+		return sysfs_emit(buf, "0\n");
+
 	return sysfs_emit(buf, "%llu\n", div_u64(ktime_to_us(m->lat_sum[READ]),
 						 m->nr_req[READ]));
 }
···
 {
 	struct ufs_hba *hba = dev_get_drvdata(dev);
 	struct ufs_hba_monitor *m = &hba->monitor;
+
+	if (!m->nr_req[WRITE])
+		return sysfs_emit(buf, "0\n");
 
 	return sysfs_emit(buf, "%llu\n", div_u64(ktime_to_us(m->lat_sum[WRITE]),
 						 m->nr_req[WRITE]));