dbc_ep_do_queue() can now get the device pointer directly from dbc
structure instead of going through the xhci_hcd structure.

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/20200723144530.9992-12-mathias.nyman@linux.intel.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>