staging: iio: ADIS16240: Remove unused include

'#include<linux/gpio.h>' isn't being used anywhere. Remove it.
Signed-off-by: Rohit Sarkar <rohitsarkar5398@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/staging/iio/accel/adis16240.c

@@ -7,7 +7,6 @@
 
 #include <linux/interrupt.h>
 #include <linux/irq.h>
-#include <linux/gpio.h>
 #include <linux/delay.h>
 #include <linux/device.h>
 #include <linux/kernel.h>