ARM: dts: imx53-qsb: Use pinctrl for gpio-led

Since commit 8fe4554f (leds: leds-gpio: adopt pinctrl support) gpio-led driver
has pinctrl support, so setup the gpio led pin via pinctrl and avoid the
following warning:

leds-gpio leds.2: pins are not configured from the driver

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Reviewed-by: Marek Vasut <marex@denx.de>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>