vmwgfx: Enable use of the vblank system

This is to avoid accessing uninitialized data during
drm_irq_uninstall and vblank ioctls. At the same time, enable error check from
drm_kms_init which previously appeared to ignore all errors.

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
index 1636e9b..e882ba0 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
@@ -996,3 +996,8 @@
 	ttm_read_unlock(&vmaster->lock);
 	return ret;
 }
+
+u32 vmw_get_vblank_counter(struct drm_device *dev, int crtc)
+{
+	return 0;
+}