mfd: twl6040: Switch to using gpiod API

This patch switches the dirver from legacy gpio API to a newer gpiod
API so that we can eventually drop the former.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/20220926054421.1546436-4-dmitry.torokhov@gmail.com