usb: musb: Change to use new IO access

Change to use new IO access. This allows us to build in multiple
MUSB glue layers.

[ balbi@ti.com : switch to EXPORT_SYMBOL_GPL()
	fix long lines ]

Cc: Fabio Baltieri <fabio.baltieri@linaro.org>
Cc: Lee Jones <lee.jones@linaro.org>
Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>