The build system uses HAVE_VENDOR_COMMON_LIB to automatically include
board/$(VENDOR)/common/Makefile, therefore let's use that to implicitly
include board/theobroma-systems/common/Makefile and compile the common.c
file when building proper.
Signed-off-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
