Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/sound/drivers/Kconfig b/sound/drivers/Kconfig
index 648a12d..09932cc 100644
--- a/sound/drivers/Kconfig
+++ b/sound/drivers/Kconfig
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
 config SND_MPU401_UART
         tristate
         select SND_RAWMIDI