tinker: Initial support (#140)

* tinker: initial support

* Fix info

* Fix uboot defconfig

* Split kernel config

* Fix name

* Add post-image

* Init different boot

* Add SPL images

* Dynamic rauc config

* Support SPL for OTA

* Fix expand script style

* Fix SPL

* Bump build u-boot

* Cleanup

* Add cmd for scritps

* Use kernel from armbian

* Fix u-boot

* Add bluetooth support

* Fix bt

* Fix env

* Change uart debug like rpi

* move config

buildroot-external/board/raspberrypi/rpi3/info

@@ -3,3 +3,4 @@ BOARD_NAME="RaspberryPi 3"
 CHASSIS=embedded
 BOOTLOADER=uboot
 KERNEL_FILE=zImage
+BOOT_SYS=mbr