configs: khadas-vim3{l}_android_ab: enable A/B support

meson64_android.h also relies on CMD_AB_SELECT so enable that as well.

Signed-off-by: Guillaume La Roque <glaroque@baylibre.com>
Signed-off-by: Mattijs Korpershoek <mkorpershoek@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Link: https://lore.kernel.org/r/20211122152207.219023-5-mkorpershoek@baylibre.com