MA-17260 Add vendor boot and boot header v3 support

MA-17260 Add vendor boot and boot header v3 support

GKI(Generic Kernel Image) would require the boot header v3 and vendor
boot support, all device specific info are moved to vendor_boot partition
,the boot header v3 will not be compatible with earlier version(0/1/2).

This commit adds support for boot header v3 and vendor boot, it would
concatenate the generic ramdisk and vendor ramdisk to generate the
final ramdisk passed to kernel.

Test: boots with or without boot header v3 and vendor boot support.

Signed-off-by: Ji Luo <ji.luo@nxp.com>
Change-Id: Ib3298ae46bfc728aa4a34909d372eff6cc86ca70
(cherry picked from commit c3854f270a19e7d57b996e6074d692ab9bc88c32)