gpio: gpio-regmap: Use devm_add_action_or_reset()

Slightly simplify the devm_gpio_regmap_register() by using the
devm_add_action_or_reset().

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Reviewed-by: Michael Walle <michael@walle.cc>
Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>