imx-drm: imx-drm-core: use the crtc drm device for vblank

There are a couple of ways to get at the drm_device for the vblank
operations.  One of them is via the private imxdrm structure, the
other is via the DRM crtc structure, which also stores a pointer.
Use the DRM method instead of our own method.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>
Acked-by: NShawn Guo <shawn.guo@linaro.org>
Tested-by: NShawn Guo <shawn.guo@linaro.org>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/imx-drm/imx-drm-core.c

@@ -142,19 +142,19 @@ EXPORT_SYMBOL_GPL(imx_drm_crtc_panel_format);
 
 int imx_drm_crtc_vblank_get(struct imx_drm_crtc *imx_drm_crtc)
 {
-	return drm_vblank_get(imx_drm_crtc->imxdrm->drm, imx_drm_crtc->pipe);
+	return drm_vblank_get(imx_drm_crtc->crtc->dev, imx_drm_crtc->pipe);
 }
 EXPORT_SYMBOL_GPL(imx_drm_crtc_vblank_get);
 
 void imx_drm_crtc_vblank_put(struct imx_drm_crtc *imx_drm_crtc)
 {
-	drm_vblank_put(imx_drm_crtc->imxdrm->drm, imx_drm_crtc->pipe);
+	drm_vblank_put(imx_drm_crtc->crtc->dev, imx_drm_crtc->pipe);
 }
 EXPORT_SYMBOL_GPL(imx_drm_crtc_vblank_put);
 
 void imx_drm_handle_vblank(struct imx_drm_crtc *imx_drm_crtc)
 {
-	drm_handle_vblank(imx_drm_crtc->imxdrm->drm, imx_drm_crtc->pipe);
+	drm_handle_vblank(imx_drm_crtc->crtc->dev, imx_drm_crtc->pipe);
 }
 EXPORT_SYMBOL_GPL(imx_drm_handle_vblank);