staging: iio: tsl2x7x: remove unnecessary struct iio_dev definition

tsl2x7x.h has a blank definition for 'struct iio_dev' that is not
needed. This patch removes that definition.
Signed-off-by: Brian Masney <masneyb@onstation.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/staging/iio/light/tsl2x7x.h

@@ -23,8 +23,6 @@
 #define __TSL2X7X_H
 #include <linux/pm.h>
 
-struct iio_dev;
-
 struct tsl2x7x_lux {
 	unsigned int ratio;
 	unsigned int ch0;