mfd: arizona: Switch to using devm_gpiod_get()

Now that gpiolib recognizes wlf,reset legacy GPIO and will handle it
even if DTS uses it without -gpio[s] suffix, we can switch to more
standard devm_gpiod_get() and later remove devm_gpiod_get_from_of_node().

Note that we will lose "arizona /RESET" custom GPIO label, but since we
do not set such custom label when using the modern binding, I opted to
not having it here either.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>