ARM: ux500: Add a ab8500-usb Device Tree node for db8500 based devices

Here we specify each of the ab8500 USB driver's seven IRQs, which the
driver references by name. We also apply regulator support for the
three used by the device.

Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>