drivers/gpu/drm/tilcdc: Makefile, only -Werror when no -W* in EXTRA_CFLAGS

When make with EXTRA_CFLAGS=-W, it will report error.
  so give a check in Makefile.

Signed-off-by: Chen Gang <gang.chen@asianux.com>
Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Acked-by: Rob Clark <robdclark@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/tilcdc/Makefile

@@ -1,4 +1,7 @@
-ccflags-y := -Iinclude/drm -Werror
+ccflags-y := -Iinclude/drm
+ifeq (, $(findstring -W,$(EXTRA_CFLAGS)))
+	ccflags-y += -Werror
+endif
 
 tilcdc-y := \
 	tilcdc_crtc.o \