docs: driver-model: Add missing managed GPIO array get functions

devm_gpiod_get_array and devm_gpiod_get_array_optional were missing
from the list. Add them.

Signed-off-by: Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Link: https://lore.kernel.org/r/f56dce4fcb71592cbcf0fc48a841f86f52770d4c.1576054779.git.matti.vaittinen@fi.rohmeurope.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>