iio: cros_ec: Drop unnecessary include files

The cros_ec sensors drivers do not call any sysfs functions
or use any sysfs defines, and thus do not need to include
linux/sysfs.h. Also, some cros_ec drivers include linux/delay.h
and is not used.

Signed-off-by: Guenter Roeck <groeck@chromium.org>
[remove linux/delay.h]
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>