platform/chrome: wilco_ec: use sysfs_emit() instead of sprintf()

Follow the advice in Documentation/filesystems/sysfs.rst:
show() should only use sysfs_emit() or sysfs_emit_at() when formatting
the value to be returned to user space.
Signed-off-by: Ai Chao <aichao@kylinos.cn>
Link: https://lore.kernel.org/r/20240314052828.186924-1-aichao@kylinos.cnSigned-off-by: Tzung-Bi Shih <tzungbi@kernel.org>

drivers/platform/chrome/wilco_ec/sysfs.c

@@ -192,7 +192,7 @@ static ssize_t usb_charge_show(struct device *dev,
 	if (ret < 0)
 		return ret;
 
-	return sprintf(buf, "%d\n", rs.val);
+	return sysfs_emit(buf, "%d\n", rs.val);
 }
 
 static ssize_t usb_charge_store(struct device *dev,