Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/drivers/rtc/rtc-generic.c b/drivers/rtc/rtc-generic.c
index 1bf5d23..89ae78e 100644
--- a/drivers/rtc/rtc-generic.c
+++ b/drivers/rtc/rtc-generic.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /* rtc-generic: RTC driver using the generic RTC abstraction
  *
  * Copyright (C) 2008 Kyle McMartin <kyle@mcmartin.ca>