xhci: dbc: Pass dbc pointer to dbc_handle_xfer_event() instead of xhci_hcd pointer

The event handling function only used xhci pointer to get the dbc pointer.
Pass the dbc pointer instead as a parameter

No functional changes
This change helps decoupling xhci and DbC

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20200723144530.9992-15-mathias.nyman@linux.intel.com


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