Add USE_OPENGL_RENDERER compile flag.

This flag defines whether the UI OpenGL renderer is compiled or not.

Change-Id: I24597d34af773389166a190506655f8486ab233f
diff --git a/BoardConfig.mk b/BoardConfig.mk
index 74491ea..c53e286 100755
--- a/BoardConfig.mk
+++ b/BoardConfig.mk
@@ -30,6 +30,8 @@
 
 BOARD_HAVE_GPS := true
 
+USE_OPENGL_RENDERER := true
+
 # needed for source compilation of nvidia libraries
 -include vendor/nvidia/proprietary_src/build/definitions.mk