Add tinker-board-s machine configuration

Asus Tinker Board-S has emmc on mmcblk1, this is also the default
configuration when building the image. If you need an image for booting
from the sd card set RK_BOOT_DEVICE to mmcblk0

Signed-off-by: Sergey Bostandzhyan <jin@mediatomb.cc>

README

@@ -16,6 +16,7 @@ Status of supported boards:
 	builds and boots gpt image:
 		rock-pi-4
 		tinker-board
+		tinker-board-s
 		vyasa-rk3288
 		firefly-rk3288
 	builds:

conf/machine/tinker-board-s.conf

@@ -0,0 +1,27 @@
+# Copyright (C) 2020  Sergey Bostandzhyan
+# Released under the MIT license (see COPYING.MIT for the terms)
+
+#@TYPE: Machine
+#@NAME: Tinker-S RK3288
+#@DESCRIPTION: ASUS Tinker Board is a Raspberry Pi 3 Alternative based on Rockchip RK3288 Processor.
+
+require conf/machine/include/rk3288.inc
+
+KERNEL_DEVICETREE = "rk3288-tinker-s.dtb"
+UBOOT_MACHINE = "tinker-s-rk3288_defconfig"
+
+RK_BOOT_DEVICE ?= "mmcblk1"
+
+WKS_FILE = "tinker-board.wks"
+IMAGE_FSTYPES += "wic wic.bmap"
+
+WKS_FILE_DEPENDS ?= " \
+    mtools-native \
+    dosfstools-native \
+    virtual/bootloader \
+    virtual/kernel \
+    "
+IMAGE_BOOT_FILES ?= "\
+    ${KERNEL_IMAGETYPE} \
+    ${KERNEL_DEVICETREE} \
+    "