staging: iio: iio_event_monitor: Add support for missing IIO modifiers

This patch adds the missing IIO modifiers in event_is_known function
and iio_modifier_names vector.

Additionally, it removes duplicate name entries of IIO_MOD_LIGHT_BOTH
and IIO_MOD_LIGHT_IR in iio_modifier_names.

Signed-off-by: Roberta Dobrescu <roberta.dobrescu@gmail.com>
Reviewed-by: Daniel Baluta <daniel.baluta@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>