The leds-gpio driver recently got pinctrl support, so setup the power
led gpio muxing through pinctrl.

This avoids the warning:
leds-gpio leds.X: pins are not configured from the driver
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>