omap3: Add external VBUS power switch and overcurrent detect onIGEP v2 board

GPIO for various devices are missing from the board initialization.
This patch adds support for the VBUS and over current gpios.  Without this
patch, input/outputs from these two sources are ignored.

Signed-off-by: Enric Balletbo i Serra <eballetbo@gmail.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>