The new "boot_android" command simply executes the Android Bootloader
flow. This receives the location (interface, dev, partition) of the
Android "misc" partition which is then used to lookup and infer the
kernel and system images that should be booted.

Bug: 32707546
Test: Booted a rpi3 build with Android Things.
Signed-off-by: Alex Deymo <deymo@google.com>

Change-Id: Ibf3f31e38b159d42db7a0835b99ad7ec260fc2a7