plat: marvell: armada: a3k: Build UART image files directly in $(BUILD_UART) subdirectory

This removes need to move files and also allows to build uart and flash
images in parallel.

Signed-off-by: Pali Rohár <pali@kernel.org>
Change-Id: I13bea547d7849615e1c1e11d333c8c99e568d3f6
1 file changed