usb: xhci: remove unused variables from struct 'xhci_hcd'

Variables 'max_slots', 'max_ports', 'isoc_threshold' and 'event_ring_max'
are never set or used. Thus, remove them.

Signed-off-by: Niklas Neronin <niklas.neronin@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20240905143300.1959279-7-mathias.nyman@linux.intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>