drm/vc4: 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/20170901144954.19620-6-thierry.reding@gmail.com

drivers/gpu/drm/vc4/Makefile

@@ -24,5 +24,3 @@ vc4-y := \
 vc4-$(CONFIG_DEBUG_FS) += vc4_debugfs.o
 
 obj-$(CONFIG_DRM_VC4)  += vc4.o
-
-CFLAGS_vc4_trace_points.o := -I$(src)

drivers/gpu/drm/vc4/vc4_trace.h

@@ -59,5 +59,5 @@ TRACE_EVENT(vc4_wait_for_seqno_end,
 
 /* This part must be outside protection */
 #undef TRACE_INCLUDE_PATH
-#define TRACE_INCLUDE_PATH .
+#define TRACE_INCLUDE_PATH ../../drivers/gpu/drm/vc4
 #include <trace/define_trace.h>