net: rfkill: gpio: convert to descriptor-based GPIO interface

Convert to the safer gpiod_* family of API functions.

Signed-off-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Tested-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>