configs: add khadas-vim3{l}_android for AOSP support

The Khadas VIM3 and VIM3L board are well supported in AOSP[1].
However, there is no mainline U-Boot support for it.
The U-Boot used in AOSP is based on a vendor tree [2]

Add all the necessary bits to flash and boot Android for both Khadas
VIM3 and VIM3L boards.

For Android instructions, refer to [1]

[1] https://source.android.com/setup/build/devices#vim3_and_vim3l_boards
[2] https://gitlab.com/baylibre/amlogic/atv/u-boot



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/20211122152207.219023-3-mkorpershoek@baylibre.com