udev: Do not consider USB WWAN ports as valid candidates

For now WWAN subsystem support has only been validated for PCI/MHI based devices and extra patches for USB based devices (qmi_wwan, cdc-mbim...) may be required, so do not consider WWAN ports being on USB bus.

Signed-off-by: Loic Poulain loic.poulain@linaro.org