OMAP7xx: GPIO: Introduce support for GPIO init

Add support for handling OMAP7xx specific gpio_init by
providing platform device data and doing device registration.

Signed-off-by: Charulatha V <charu@ti.com>
Acked-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>