Use mkqcdbootimg to create boot image.

On Sony's OpenSource website actually there's a guide that says
to include mkqcdbootimg repository in local_manifests. Also, it
states that the system should compile successfully like that
and that was not the case with tianchi.
This will fix the problem.
Set correct BOARD_RAMDISK_OFFSET. Use vars for mkbootimg args.

Actually, the main yukon BoardConfig sets BOARD_RAMDISK_OFFSET
as 0x02000000. Tianchi needs 0x03000000.
Specify DT version in mkbootimg args.