pinctrl: imx: fix using pin->input_val wrongly

The commit: "pinctrl: imx: Use struct type for pins" relaced
pin->input_reg by pin->input_val wrongly, fix it at this commit.

Signed-off-by: Peter Chen <peter.chen@freescale.com>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>