Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/drivers/rtc/rtc-r7301.c b/drivers/rtc/rtc-r7301.c
index 1943c81..2498278 100644
--- a/drivers/rtc/rtc-r7301.c
+++ b/drivers/rtc/rtc-r7301.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * EPSON TOYOCOM RTC-7301SF/DG Driver
  *