xhci: xhci-ring: use port structures for port event handler

use port structures in the port event handler.
Getting the right hcd and hcd portnumber from the hardware port number
is a lot easier with port structures, and allows us to remove a lot
of the previous code, including the find_faked_portnum_from_hw_index()
function

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>