mb/system76/tgl-u/Makefile.inc: Remove path to non-existent folder

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

Change-Id: Ie0e31fcdbeb219d3ecbe14a492d3e7824f6a51cc
Signed-off-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/70397
Reviewed-by: Tim Crawford <tcrawford@system76.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
diff --git a/src/mainboard/system76/tgl-u/Makefile.inc b/src/mainboard/system76/tgl-u/Makefile.inc
index ff90842..845c39a 100644
--- a/src/mainboard/system76/tgl-u/Makefile.inc
+++ b/src/mainboard/system76/tgl-u/Makefile.inc
@@ -1,5 +1,8 @@
 CPPFLAGS_common += -I$(src)/mainboard/$(MAINBOARDDIR)/include
+
+ifeq ($(CONFIG_BOARD_SYSTEM76_GALP5),y)
 CPPFLAGS_common += -I$(src)/mainboard/$(MAINBOARDDIR)/variants/$(VARIANT_DIR)/include
+endif
 
 bootblock-y += bootblock.c
 bootblock-y += variants/$(VARIANT_DIR)/gpio_early.c