pinctrl: sx150x: Register pinctrl before adding the gpiochip

Various gpiolib activity depend on the pinctrl to be up and kicking.
Therefore, register the pinctrl before adding a gpiochip.

Cc: stable@vger.kernel.org
Suggested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Peter Rosin <peda@axentia.se>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>