gralloc: Add debug.gralloc.gfx_ubwc_disable

This patch adds a new debug property
that can be used to disable UBWC compilant
allocations for graphics stack by gralloc.

Change-Id: I59e5994700730c73d62eec9f74ab6ded60c2d256
diff --git a/libgralloc/gr.h b/libgralloc/gr.h
index 5ee0cf8..1a10532 100644
--- a/libgralloc/gr.h
+++ b/libgralloc/gr.h
@@ -148,6 +148,8 @@
     ADRENOPIXELFORMAT getGpuPixelFormat(int hal_format);
 
     private:
+        // Overriding flag to disable UBWC alloc for graphics stack
+        int  gfx_ubwc_disable;
         // Pointer to the padding library.
         void *libadreno_utils;