xhci: save slot ID in struct 'xhci_port'

xhci: save slot ID in struct 'xhci_port'

Slot ID is a index of a virtual device in struct 'xhci_hcd->devs[]'.
Previously, to get the slot ID associated with a port, we had to loop
through all devices and compare ports, which is very inefficient.
Instead, the slot ID (of the device which is directly connected to the
port), is added to the its corresponding 'xhci_port' struct. As a result,
finding the port's device is quick and easy.

Function 'xhci_find_slot_id_by_port()' is removed, as it is no longer
needed.

Signed-off-by: Niklas Neronin <niklas.neronin@intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20240229141438.619372-4-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>