iio: proximity: as3935: move storm out of range check

Move out of storm check to apply to IIO_CHAN_INFO_RAW so the reported
results are constant between the former and the IIO_CHAN_INFO_PROCESSED

Signed-off-by: Matt Ranostay <matt.ranostay@konsulko.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>