ARM: OMAP: USB: Change omap USB code to use omap_read/write instead of __REG

Change omap USB code to use omap_read/write instead of __REG for multi-omap

Cc: David Brownell <david-b@pacbell.net>
Cc: linux-usb@vger.kernel.org
Cc: i2c@lm-sensors.org
Signed-off-by: Tony Lindgren <tony@atomide.com>