omap: 4430sdp board support for proximity sensor

omap 4430sdp board support for the  proximity sensor via GPIO keys.
The proximity sensor is connected to GPIO and is registered as a
GPIO key.
- Making the default state of the sensor off at bootup
- The init is called before platform_add_devices

Signed-off-by: Shubhrajyoti D <shubhrajyoti@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>