staging: iio: adis16220_core.c: add module.h

This is needed and makes the linux-next merge easier.
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Jonathan Cameron <jic23@cam.ac.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/iio/accel/adis16220_core.c

@@ -13,6 +13,7 @@
 #include <linux/spi/spi.h>
 #include <linux/slab.h>
 #include <linux/sysfs.h>
+#include <linux/module.h>
 
 #include "../iio.h"
 #include "../sysfs.h"