[ARM] tegra: add GPIO support

v2: fixes from Mike Rapoport:
	- move gpio-names.h to arch/arm/mach-tegra
    fixes from Russell King
	- include linux/io.h and linux/gpio.h instead of asm/io.h
	  and asm/gpio.h
    additional changes:
    	- add macros to convert between irq and gpio numbers for platform data
	- change for_each_bit to for_each_set_bit in gpio.c
v3:
	- minor bugfixes

Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: Erik Gilling <konkers@android.com>