CONFIG_OF_EMBED is intended for debugging and is not recommended for
production devices. Remove it from the Nokia XG-040G-MD defconfig so
Kconfig selects CONFIG_OF_SEPARATE, consistent with the other Airoha
boards.
The existing default device tree and u-boot.bin build target ensure that
the separate DTB is built and appended to the deployable U-Boot image.
Signed-off-by: Robert Marko <robert.marko@sartura.hr>