Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/powerpc/kernel/ucall.S b/arch/powerpc/kernel/ucall.S
new file mode 100644
index 0000000..07296bc
--- /dev/null
+++ b/arch/powerpc/kernel/ucall.S
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Generic code to perform an ultravisor call.
+ *
+ * Copyright 2019, IBM Corporation.
+ *
+ */
+#include <asm/ppc_asm.h>
+#include <asm/export.h>
+
+_GLOBAL(ucall_norets)
+EXPORT_SYMBOL_GPL(ucall_norets)
+	sc	2	/* Invoke the ultravisor */
+	blr		/* Return r3 = status */