ARM: imx: eliminate macro IRQ_GPIOx()

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

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