xhci: cleanup xhci_hub_control port references

Both port number and port structure of a port are referred to several
times when handing hub requests in xhci.

Use more suitable data types and readable names for these.
Cleanup only, no functional changes

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20230202150505.618915-6-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>