usb: cdns3: host: add xhci_plat_priv quirk XHCI_SKIP_PHY_INIT

cdns3 manages PHY by own DRD driver, so skip the management by
HCD core.

Reviewed-by: Jun Li <jun.li@nxp.com>
Reviewed-by: Pawel Laszczak <pawell@cadence.com>
Signed-off-by: Peter Chen <peter.chen@nxp.com>