configs: meson64_android: implement recovery boot via BCB

Right now meson64_android does not know how to boot into Android
Recovery: it simply falls back to "fastboot" mode in the bootloader.

Implement the boot to recovery.
While at it, use the standard BCB way instead of a sm for consistency.

Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Acked-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>