arm: meson: board-gx: Setup VPU in fdt

If VIDEO_MESON is enabled, we need to setup the fdt for the framebuffer.

Call meson_vpu_rsv_fb() which reserves the framebuffer memory region for
EFI, and sets up simple-framebuffer nodes if simplefb support is
enabled.

Signed-off-by: Maxime Jourdan <mjourdan@baylibre.com>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
Reviewed-by: Anatolij Gustschin <agust@denx.de>