iio staging: fix spelling of suppression in isl29018

beware, does change the ABI as proximity_on_chip_ambient_infrared_supression
is changed to proximity_on_chip_ambient_infrared_suppression

Signed-off-by: Peter Meerwald <pmeerw@pmeerw.net>
Acked-by: Jonathan Cameron <jic23@kernel.org>
Acked-by: Laxman Dewangan <ldewangan@nvidia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>