drm_hwcomposer: Allow importer to be specified from BoardConfig

Use BOARD_DRM_HWCOMPOSER_BUFFER_IMPORTER from BoardConfig to
determine which importer to use.

Signed-off-by: Sean Paul <seanpaul@chromium.org>
Change-Id: Ia081628830b78187ea1f8a3e3e4260188e130324
diff --git a/Android.mk b/Android.mk
index 58bf1ef..81e7e48 100644
--- a/Android.mk
+++ b/Android.mk
@@ -17,9 +17,6 @@
 LOCAL_PATH := $(call my-dir)
 include $(CLEAR_VARS)
 
-# TODO: We should specify this in device.mk
-BUFFER_IMPORTER := nvidia-gralloc
-
 LOCAL_SHARED_LIBRARIES := \
 	libcutils \
 	libdrm \
@@ -47,11 +44,11 @@
 	hwcomposer.cpp \
 	worker.cpp
 
-ifeq ($(strip $(BUFFER_IMPORTER)),drm-gralloc)
+ifeq ($(strip $(BOARD_DRM_HWCOMPOSER_BUFFER_IMPORTER)),drm-gralloc)
 LOCAL_C_INCLUDES += external/drm_gralloc
 LOCAL_SRC_FILES += hwcomposer_import_drm_gralloc.cpp
 endif
-ifeq ($(strip $(BUFFER_IMPORTER)),nvidia-gralloc)
+ifeq ($(strip $(BOARD_DRM_HWCOMPOSER_BUFFER_IMPORTER)),nvidia-gralloc)
 LOCAL_C_INCLUDES += external/drm_gralloc
 LOCAL_SRC_FILES += hwcomposer_import_nv_gralloc.cpp
 endif