ENGR00251209-2 usb: otg: fix the dp/dm will be floating when phy is no 3v3

ENGR00251209-2 usb: otg: fix the dp/dm will be floating when phy is no 3v3

For the design which the phy is no power (no 5v for VBUS), the
PHY can't get dp/dm correctly, so it the port change interrpt
is enabled or the host enters low power mode, the unexpected
interrupt will occur.
This commit will make the dp/dm as zero at otg configuration.
For gadget-only, the same function is existed at probe.
For host-only, the vbus will be on before port change interrupt
is enabled.

Signed-off-by: Peter Chen <peter.chen@freescale.com>