read the gpio directory structure

Read the gpio directory structure where we will read the different
data we are interested in.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
diff --git a/Makefile b/Makefile
index 8d41b24..2da9d67 100644
--- a/Makefile
+++ b/Makefile
@@ -4,7 +4,7 @@
 CFLAGS?=-O1 -g -Wall -Wshadow
 CC?=gcc
 
-OBJS = powerdebug.o sensor.o clocks.o regulator.o \
+OBJS = powerdebug.o sensor.o clocks.o regulator.o gpio.o \
 	display.o tree.o utils.o mainloop.o
 
 default: powerdebug