xhci: add helper that checks for unhandled events on a event ring

Add unhandled_event_trb() that returns true in case xHC hardware has
written new event trbs to the event ring that driver has not yet handled.

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com>
Link: https://lore.kernel.org/r/20240217001017.29969-8-quic_wcheng@quicinc.com


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