Makefiles: Use $(MAINBOARD_DIR) instead of $(CONFIG_MAINBOARD_DIR)

The variable MAINBOARD_DIR already has the quotes stripped off.

Change-Id: Ib434ce92bdbc49180fb3f713b26d65ba4cf8c441
Signed-off-by: Martin Roth <martinroth@chromium.org>
Reviewed-on: https://review.coreboot.org/16117
Tested-by: build bot (Jenkins)
Reviewed-by: Lee Leahy <leroy.p.leahy@intel.com>
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
3 files changed