usb: otg: twl4030-usb: poll for ID disconnect

On pandora, STS_USB interrupt doesn't arrive on USB host cable disconnect
for some reason while VBUS is driven by twl itself, but STS_HW_CONDITIONS
is updated correctly. It does work fine when PHY is powered down though.
To work around that we have to poll.

TI PSP kernels have similar workarounds, so (many?) more boards are likely
affected.