pinctrl: ingenic: Handle PIN_CONFIG_OUTPUT config

This makes the driver support the 'output-low' and 'output-high'
devicetree properties in gpio-hog sub-nodes.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
Link: https://lore.kernel.org/r/20191119155211.102527-1-paul@crapouillou.net
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>