Revert "bcm2708: fix gpio_to_irq() name clash"

This reverts commit e59870081d5f6af31e77078dec77a8343daddb47.

Conflicts:
	arch/arm/mach-bcm2708/bcm2708_gpio.c
Merge pull request #506 from jfasch/rpi-3.11.y-fix-gpio_to_irq

Please pull: NEED_MACH_GPIO_H vs. gpio_to_irq() woes