iio: light: rpr0521 poweroff for probe fails

Set sensor measurement off after probe fail in pm_runtime_set_active() or
iio_device_register(). Without this change sensor measurement stays on
even though probe fails on these calls.

This is maybe rare case, but causes constant power drain without any
benefits when it happens. Power drain is 20-500uA, typically 180uA.

Signed-off-by: Mikko Koivunen <mikko.koivunen@fi.rohmeurope.com>
Acked-by: Daniel Baluta <daniel.baluta@nxp.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>