xhci: dbc: Flush queued requests before stopping dbc

xhci: dbc: Flush queued requests before stopping dbc

Flush dbc requests when dbc is stopped and transfer rings are freed.
Failure to flush them lead to leaking memory and dbc completing odd
requests after resuming from suspend, leading to error messages such as:

[   95.344392] xhci_hcd 0000:00:0d.0: no matched request

Cc: stable <stable@kernel.org>
Fixes: dfba2174dc42 ("usb: xhci: Add DbC support in xHCI driver")
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Link: https://lore.kernel.org/r/20250627144127.3889714-5-mathias.nyman@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>