mb/intel/coffeelake_rvp/Makefile.inc: Avoid link to non-existent folder

Found using 'Wmissing-include-dirs' command option.

Change-Id: I178c849d07e61d7a237629f3be1b52d3b4abb513
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/70459
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
diff --git a/src/mainboard/intel/coffeelake_rvp/Makefile.inc b/src/mainboard/intel/coffeelake_rvp/Makefile.inc
index 77f0691..57e73bc 100644
--- a/src/mainboard/intel/coffeelake_rvp/Makefile.inc
+++ b/src/mainboard/intel/coffeelake_rvp/Makefile.inc
@@ -16,4 +16,6 @@
 CPPFLAGS_common += -I$(src)/mainboard/$(MAINBOARDDIR)/variants/baseboard/include
 
 subdirs-y += variants/$(VARIANT_DIR)
+ifeq ($(CONFIG_BOARD_INTEL_COMETLAKE_RVPU)$(CONFIG_BOARD_INTEL_WHISKEYLAKE_RVP),y)
 CPPFLAGS_common += -I$(src)/mainboard/$(MAINBOARDDIR)/variants/$(VARIANT_DIR)/include
+endif