drm: Use correct path to trace include

The header comment in include/trace/define_trace.h specifies that the
TRACE_INCLUDE_PATH needs to be relative to the define_trace.h header
rather than the trace file including it. Most instances get that wrong
and work around it by adding the $(src) directory to the include path.

While this works, it is preferable to refer to the correct path to the
trace file in the first place and avoid any workaround.
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170901144954.19620-1-thierry.reding@gmail.com

drivers/gpu/drm/Makefile

@@ -44,8 +44,6 @@ drm_kms_helper-$(CONFIG_DRM_DP_AUX_CHARDEV) += drm_dp_aux_dev.o
 obj-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o
 obj-$(CONFIG_DRM_DEBUG_MM_SELFTEST) += selftests/
 
-CFLAGS_drm_trace_points.o := -I$(src)
-
 obj-$(CONFIG_DRM)	+= drm.o
 obj-$(CONFIG_DRM_MIPI_DSI) += drm_mipi_dsi.o
 obj-$(CONFIG_DRM_ARM)	+= arm/

drivers/gpu/drm/drm_trace.h

@@ -61,5 +61,5 @@ TRACE_EVENT(drm_vblank_event_delivered,
 
 /* This part must be outside protection */
 #undef TRACE_INCLUDE_PATH
-#define TRACE_INCLUDE_PATH .
+#define TRACE_INCLUDE_PATH ../../drivers/gpu/drm
 #include <trace/define_trace.h>