omap3: igep3: Add USB EHCI support for IGEP module

The OMAP3 IGEP module has one EHCI interface on board using
USB2HS port. GPIO183 is used as PHY reset.

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