extcon: Remove duplicate inclusion of extcon.h header file

extcon.h header file was included twice.
Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
Signed-off-by: Sachin Kamat <sachin.kamat@samsung.com>
Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>

drivers/extcon/extcon-gpio.c

@@ -26,7 +26,6 @@
 #include <linux/interrupt.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>
-#include <linux/extcon.h>
 #include <linux/workqueue.h>
 #include <linux/gpio.h>
 #include <linux/extcon.h>