gpio: max730x: use devres to shrink and simplify code

Use managed variants of gpiochip_add_data() and mutex_init() to drop a
label and lose a couple LOC.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20241017121447.73754-1-brgl@bgdev.pl


Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>