MA-15339-1 load ramdisk in boot image to do first stage mount

MA-15339-1 load ramdisk in boot image to do first stage mount

With Android10 code, to build GSI image for devices launching with
Android10, the target should be "aosp_$arch-user". Google releases GSI
images is so built in user mode.

To do CTS-on-GSI test, a debug ramdisk containing .prop file to enable
adb root permission and GSI keys to verify the GSI image is needed, this
ramdisk is in boot image. so ramdisk in boot image need to be loaded by
uboot even in non-recovery mode.

To save boot time, only standard Android use ramdisk to boot up Android,
Android Auto keeps the original way: kernel be responsible for verify
and mount system partition. Let the customers to decide whether to use
recovery ramdisk to boot the system. and under this condition, user-debug
Android Auto GSI image need to be used for VTS-on-GSI test.

when use ramdisk to bootup Android, info provided by "dm=" bootarg is
not used by kernel to setup dm-verity, so it is removed from the
bootargs. The 4.19 kernel used together with this uboot does not handle
"skip_initramfs", so it's also removed.

Change-Id: Ia8b8fa8b85a44acda2670b46504038a009ce01a8
Signed-off-by: faqiang.zhu <faqiang.zhu@nxp.com>