Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/arch/mips/sibyte/common/dma.c b/arch/mips/sibyte/common/dma.c
new file mode 100644
index 0000000..eb47a94
--- /dev/null
+++ b/arch/mips/sibyte/common/dma.c
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ *	DMA support for Broadcom SiByte platforms.
+ *
+ *	Copyright (c) 2018  Maciej W. Rozycki
+ */
+
+#include <linux/swiotlb.h>
+#include <asm/bootinfo.h>
+
+void __init plat_swiotlb_setup(void)
+{
+	swiotlb_init(1);
+}