OMAP2+: GPIO: device registration

OMAP2+: GPIO: device registration

Use omap_device_build() API to do platform_device_register of
GPIO devices. For OMAP2+ chips, the device specific data defined
in the centralized hwmod database will be used.

gpio_init needs to be done before machine_init functions access
gpio APIs. Hence gpio_init is made as a postcore_initcall.

Signed-off-by: Charulatha V <charu@ti.com>
Acked-by: Benoit Cousson <b-cousson@ti.com>
Reviewed-by: Basak, Partha <p-basak2@ti.com>
Acked-by: Kevin Hilman <khilman@deeprootsystems.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>