usb: Add tunnel_mode parameter to usb device structure

usb: Add tunnel_mode parameter to usb device structure

Add 'tunnel_mode' enum to usb device structure to describe if a USB3
link is tunneled over USB4, or connected directly using native USB2/USB3
protocols.

Tunneled devices depend on USB4 NHI host to maintain the tunnel.
Knowledge about tunneled devices is important to ensure correct
suspend and resume order between USB4 hosts and tunneled devices.
i.e. make sure tunnel is up before the USB device using it resumes.

USB hosts such as xHCI may have vendor specific ways to detect tunneled
connections. This 'tunnel_mode' parameter can be set by USB3 host driver
during hcd->driver->update_device(hcd, udev) callback.

tunnel_mode can be set to:
USB_LINK_UNKNOWN = 0
USB_LINK_NATIVE
USB_LINK_TUNNELED

USB_LINK_UNKNOWN is used in case host is not capable of detecting
tunneled links.

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20240830152630.3943215-3-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>