ARM: imx: eliminate macro IMX_GPIO_TO_IRQ()

This patch changes all the static gpio irq number assigning with
IMX_GPIO_TO_IRQ() to run-time assigning with gpio_to_irq call, and
in turn eliminates the macro IMX_GPIO_TO_IRQ().

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>