staging: iio: tsl2x7x: use either direction for IIO_EV_INFO_{ENABLE,PERIOD}
The events IIO_EV_INFO_VALUE and IIO_EV_INFO_ENABLE currently have a
falling and rising direction configured. There does not need to be a
separate distinction so this patch changes these to use the
either direction. Directory listing of event sysfs attributes for a
TSL2772 with this patch applied: