gralloc_gbm: add .lock_ycbcr to support video playback use case

The .lock_ycbcr function hook is currently missing from gralloc driver,
and that stops video playback from working.  Add a .lock_ycbcr function
implementation to get SW video playback test start working, where
HAL_PIXEL_FORMAT_YV12 format is used/tested.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
[AmitP: Verified by playing a mp4 format file using s/w codec
        (medaswcodec) on db845c running AOSP.]
Signed-off-by: Amit Pundir <amit.pundir@linaro.org>
Change-Id: I847db96bc3a08ad746560881d31cf296a5943cbf
diff --git a/gralloc/gralloc_gbm_priv.h b/gralloc/gralloc_gbm_priv.h
index d0326c5..cbe9256 100644
--- a/gralloc/gralloc_gbm_priv.h
+++ b/gralloc/gralloc_gbm_priv.h
@@ -45,6 +45,8 @@
 
 int gralloc_gbm_bo_lock(buffer_handle_t handle, int usage, int x, int y, int w, int h, void **addr);
 int gralloc_gbm_bo_unlock(buffer_handle_t handle);
+int gralloc_gbm_bo_lock_ycbcr(buffer_handle_t handle, int usage,
+		int x, int y, int w, int h, struct android_ycbcr *ycbcr);
 
 struct gbm_device *gbm_dev_create(void);
 void gbm_dev_destroy(struct gbm_device *gbm);