Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/riscv/Kbuild b/arch/riscv/Kbuild
new file mode 100644
index 0000000..d1d0aa7
--- /dev/null
+++ b/arch/riscv/Kbuild
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+obj-y += kernel/ mm/ net/