usb: phy: mxs: Add VF610 USB PHY support

This adds support for the USB PHY in Vybrid VF610. We assume that
the disconnection without VBUS is also needed for Vybrid.

Tests showed, without MXS_PHY_NEED_IP_FIX, enumeration of devices
behind a USB Hub fails with errors:

[  215.163507] usb usb1-port1: cannot reset (err = -32)
[  215.170498] usb usb1-port1: cannot reset (err = -32)
[  215.185120] usb usb1-port1: cannot reset (err = -32)
[  215.191345] usb usb1-port1: cannot reset (err = -32)
[  215.202487] usb usb1-port1: cannot reset (err = -32)
[  215.207718] usb usb1-port1: Cannot enable. Maybe the USB cable is bad?
[  215.219317] usb usb1-port1: unable to enumerate USB device

Hence we also enable the MXS_PHY_NEED_IP_FIX flag.

Acked-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Felipe Balbi <balbi@ti.com>