ptp: replace snprintf with sysfs_emit

coccinelle report:
./drivers/ptp/ptp_sysfs.c:17:8-16:
WARNING: use scnprintf or sprintf
./drivers/ptp/ptp_sysfs.c:390:8-16:
WARNING: use scnprintf or sprintf

Use sysfs_emit instead of scnprintf or sprintf makes more sense.
Reported-by: NZeal Robot <zealci@zte.com.cn>
Signed-off-by: NYang Guang <yang.guang5@zte.com.cn>
Signed-off-by: NDavid Yang <davidcomponentone@gmail.com>
Acked-by: NRichard Cochran <richardcochran@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/ptp/ptp_sysfs.c

@@ -14,7 +14,7 @@ static ssize_t clock_name_show(struct device *dev,
 			       struct device_attribute *attr, char *page)
 {
 	struct ptp_clock *ptp = dev_get_drvdata(dev);
-	return snprintf(page, PAGE_SIZE-1, "%s\n", ptp->info->name);
+	return sysfs_emit(page, "%s\n", ptp->info->name);
 }
 static DEVICE_ATTR_RO(clock_name);
 
@@ -387,7 +387,7 @@ static ssize_t ptp_pin_show(struct device *dev, struct device_attribute *attr,
 
 	mutex_unlock(&ptp->pincfg_mux);
 
-	return snprintf(page, PAGE_SIZE, "%u %u\n", func, chan);
+	return sysfs_emit(page, "%u %u\n", func, chan);
 }
 
 static ssize_t ptp_pin_store(struct device *dev, struct device_attribute *attr,