ARM: OMAP: Fix gpio by switching to generic gpio calls, v2

Fix compile by removing remaining omap specific gpio
calls. Based on earlier patches by Jarkko Nikula.

Also remove old GPIO key code, there is already a patch
to do this with gpio_keys.

Signed-off-by: Jarkko Nikula <jarkko.nikula@nokia.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>