xhci: Add a global command queue

Create a list to store command structures, add a structure to it every time
a command is submitted, and remove it from the list once we get a
command completion event matching the command.

Callers that wait for completion will free their command structures themselves.
The other command structures are freed in the command completion event handler.

Also add a check that prevents queuing commands if host is dying

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/xhci.h

@@ -1484,6 +1484,7 @@ struct xhci_hcd {
 #define CMD_RING_STATE_ABORTED         (1 << 1)
 #define CMD_RING_STATE_STOPPED         (1 << 2)
 	struct list_head        cancel_cmd_list;
+	struct list_head        cmd_list;
 	unsigned int		cmd_ring_reserved_trbs;
 	struct xhci_ring	*event_ring;
 	struct xhci_erst	erst;
@@ -1851,6 +1852,7 @@ int xhci_cancel_cmd(struct xhci_hcd *xhci, struct xhci_command *command,
 		union xhci_trb *cmd_trb);
 void xhci_ring_ep_doorbell(struct xhci_hcd *xhci, unsigned int slot_id,
 		unsigned int ep_index, unsigned int stream_id);
+void xhci_cleanup_command_queue(struct xhci_hcd *xhci);
 
 /* xHCI roothub code */
 void xhci_set_link_state(struct xhci_hcd *xhci, __le32 __iomem **port_array,