copybit: Export c2d header

On open source builds, adreno libs don't get built, due to which
c2d headers aren't exported. Export it from the display HAL.

Change-Id: I6ed1d1fcf3f99ba83d5f194e40d0b42bd7b4d566
diff --git a/libcopybit/Android.mk b/libcopybit/Android.mk
index b3d4249..2ac7d15 100644
--- a/libcopybit/Android.mk
+++ b/libcopybit/Android.mk
@@ -17,7 +17,7 @@
 include $(CLEAR_VARS)
 
 LOCAL_COPY_HEADERS_TO         := $(common_header_export_path)
-LOCAL_COPY_HEADERS            := copybit.h copybit_priv.h
+LOCAL_COPY_HEADERS            := copybit.h copybit_priv.h c2d2.h
 #Copy the headers regardless of whether copybit is built
 include $(BUILD_COPY_HEADERS)