pinctrl: bcm: nsp: implement get_direction

pinctrl: bcm: nsp: implement get_direction

The get_direction api is strongly recommended to be implemented. In fact
if it is not implemented gpio-hogs will not get the correct direction.
Add an implementation of get_direction for the nsp-gpio driver.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Link: https://lore.kernel.org/r/20191104001819.2300-3-chris.packham@alliedtelesis.co.nz
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>