Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/drivers/gpu/drm/arc/Makefile b/drivers/gpu/drm/arc/Makefile
index 73de56a..c7028b7 100644
--- a/drivers/gpu/drm/arc/Makefile
+++ b/drivers/gpu/drm/arc/Makefile
@@ -1,2 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
 arcpgu-y := arcpgu_crtc.o arcpgu_hdmi.o arcpgu_sim.o arcpgu_drv.o
 obj-$(CONFIG_DRM_ARCPGU) += arcpgu.o