tools: mktplinkfw2: add split-uboot layout

This commit adds the split-uboot partition layout used by the
Archer C50 v4 to mktplinkfw2.

Signed-off-by: David Bauer <mail@david-bauer.net>

tools/firmware-utils/src/mktplinkfw2.c

@@ -146,6 +146,12 @@ static struct flash_layout layouts[] = {
 		.kernel_la	= 0x80000000,
 		.kernel_ep	= 0x80000000,
 		.rootfs_ofs	= 0x140000,
+	}, {
+		.id		= "8MSUmtk", /* Split U-Boot OS */
+		.fw_max_len	= 0x770000,
+		.kernel_la	= 0x80000000,
+		.kernel_ep	= 0x80000000,
+		.rootfs_ofs	= 0x140000,
 	}, {
 		.id		= "8MLmtk",
 		.fw_max_len	= 0x7b0000,