add mbtk gpio api.

Change-Id: I1e1dd810465627f795242d22248191c01af58add
diff --git a/mbtk/libmbtk_lib/Makefile b/mbtk/libmbtk_lib/Makefile
index efa293c..8183ffd 100755
--- a/mbtk/libmbtk_lib/Makefile
+++ b/mbtk/libmbtk_lib/Makefile
@@ -46,7 +46,8 @@
 	src/ringbuffer.c \
 	src/mbtk_mtd.c \
 	src/mbtk_device_info.c \
-	src/mbtk_version.c
+	src/mbtk_version.c \
+	src/mbtk_gpio.c
 
 ifeq ($(MBTK_DUMP_SUPPORT), y)
 LOCAL_SRC_FILES += src/mbtk_debug.c