drivers: sensor: wsen_itds: Update driver to use gpio_dt_spec

Move driver to use gpio_dt_spec for GPIO interrupt handling.  Since
the driver can support multiple instances its possible that some
have irq's in dts and some don't.  So we add a check in
itds_trigger_set to make sure we have a GPIO device if we are
trying to set a trigger.

Signed-off-by: Kumar Gala <galak@kernel.org>