mach-ux500: musb: now musb is always in OTG mode

This change is needed after 62285963 "usb: musb: drop a
gigantic amount of ifdeferry", where CONFIG_USB_MUSB_PERIPHERAL
& CONFIG_USB_MUSB_HOST has been removed.

Signed-off-by: Philippe Langlais <philippe.langlais@linaro.org>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>