ARM: meson: enable USB DFU + RAM on Amlogic boards with USB Gadget

Enable DFU as an alternate USB boot method when script wasn't
uploaded, this fixes USB full boot on G12/SM1 boards.

Link: https://lore.kernel.org/r/20231023-usb-dfu-boot-v1-4-df9d121c67c1@linaro.org


[narmstrong: remove dfu from ad401]
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>