usb: musb: add support for ux500 platform

Initial support for u8500 and u5500 platform.

Signed-off-by: Mian Yousaf Kaukab <mian.yousaf.kaukab@stericsson.com>
Acked-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>