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 <[e-mail]>
Acked-by: Daniel Vetter <[e-mail]>
Signed-off-by: Thierry Reding <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/vc4/Makefile

···
 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

···
 
 /* 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>