drm/msm: fix build error with W=1

Combining -Werror with all the extra warning flags that W=1 adds doesn't
go so well.  Especially because some of the warnings triggered are from
included headers.  So just drop -Werror.
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/Makefile

 ccflags-y := -Iinclude/drm -Idrivers/gpu/drm/msm
-ifeq (, $(findstring -W,$(EXTRA_CFLAGS)))
-	ccflags-y += -Werror
-endif
 
 msm-y := \
 	adreno/adreno_device.o \