drm: add vblank event trace point

Emit a trace point for vblank events.  This can be helpful for mapping
drawing activity against the vblank frequency and period.

Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/Makefile

@@ -11,7 +11,8 @@ drm-y       :=	drm_auth.o drm_buffer.o drm_bufs.o drm_cache.o \
 		drm_agpsupport.o drm_scatter.o ati_pcigart.o drm_pci.o \
 		drm_sysfs.o drm_hashtab.o drm_sman.o drm_mm.o \
 		drm_crtc.o drm_modes.o drm_edid.o \
-		drm_info.o drm_debugfs.o drm_encoder_slave.o
+		drm_info.o drm_debugfs.o drm_encoder_slave.o \
+		drm_trace_points.o
 
 drm-$(CONFIG_COMPAT) += drm_ioc32.o
 
@@ -19,6 +20,8 @@ drm_kms_helper-y := drm_fb_helper.o drm_crtc_helper.o drm_dp_i2c_helper.o
 
 obj-$(CONFIG_DRM_KMS_HELPER) += drm_kms_helper.o
 
+CFLAGS_drm_trace_points.o := -I$(src)
+
 obj-$(CONFIG_DRM)	+= drm.o
 obj-$(CONFIG_DRM_TTM)	+= ttm/
 obj-$(CONFIG_DRM_TDFX)	+= tdfx/