leds: leds-gpio: Let device core handle pinctrl

Since commit ab78029e (drivers/pinctrl: grab default handles from device core)
we can rely on device core for handling pinctrl, so remove
devm_pinctrl_get_select_default() from the driver.

Reported-by: Stephen Warren <warren@wwwdotorg.org>
Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>