gralloc: Add gralloc perform api to query RGB data address

A client can call GRALLOC_MODULE_PERFORM_GET_RGB_DATA_ADDRESS api
to get RGB data address for any linear or UBWC aligned RGB buffer.

Change-Id: I3a7d25f504b7ba1dec79cc872cafbb38ddbb6bd2
diff --git a/libgralloc/gr.h b/libgralloc/gr.h
index 5ee0cf8..7dbf6c5 100644
--- a/libgralloc/gr.h
+++ b/libgralloc/gr.h
@@ -71,6 +71,7 @@
 int alloc_buffer(private_handle_t **pHnd, int w, int h, int format, int usage);
 void free_buffer(private_handle_t *hnd);
 int getYUVPlaneInfo(private_handle_t* pHnd, struct android_ycbcr* ycbcr);
+int getRgbDataAddress(private_handle_t* pHnd, void* rgb_data);
 
 // To query if UBWC is enabled, based on format and usage flags
 bool isUBwcEnabled(int format, int usage);