greybus: gpio: Create separate module

Create separate module for gpio gpbridge driver.

Tested on EVT 1.5 by inserting GP test module, all the devices were
enumerated correctly.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
diff --git a/drivers/staging/greybus/Makefile b/drivers/staging/greybus/Makefile
index 43c0c99..e5c784d 100644
--- a/drivers/staging/greybus/Makefile
+++ b/drivers/staging/greybus/Makefile
@@ -18,7 +18,6 @@
 		sdio.o	\
 		uart.o	\
 		pwm.o	\
-		gpio.o	\
 		i2c.o	\
 		spi.o	\
 		usb.o
@@ -40,6 +39,7 @@
 gb-audio-manager-y += audio_manager_module.o
 gb-camera-y := camera.o
 gb-firmware-y := fw-core.o fw-download.o
+gb-gpio-y := gpio.o
 
 obj-m += greybus.o
 obj-m += gb-phy.o
@@ -62,6 +62,7 @@
 obj-m += gb-audio-apbridgea.o
 obj-m += gb-audio-manager.o
 obj-m += gb-firmware.o
+obj-m += gb-gpio.o
 
 KERNELVER		?= $(shell uname -r)
 KERNELDIR 		?= /lib/modules/$(KERNELVER)/build