usb: dwc3: gadget: add a per-endpoint request queue lock

This will allow us to process several endpoints at a
time by making sure that we lock only shared
resources.
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/core.h

@@ -482,6 +482,7 @@ struct dwc3_event_buffer {
  * @endpoint: usb endpoint
  * @pending_list: list of pending requests for this endpoint
  * @started_list: list of started requests on this endpoint
+ * @lock: spinlock for endpoint request queue traversal
  * @regs: pointer to first endpoint register
  * @trb_pool: array of transaction buffers
  * @trb_pool_dma: dma address of @trb_pool
@@ -504,6 +505,7 @@ struct dwc3_ep {
 	struct list_head	pending_list;
 	struct list_head	started_list;
 
+	spinlock_t		lock;
 	void __iomem		*regs;
 
 	struct dwc3_trb		*trb_pool;

drivers/usb/dwc3/gadget.c

@@ -1845,6 +1845,7 @@ static int dwc3_gadget_init_hw_endpoints(struct dwc3 *dwc,
 				(epnum & 1) ? "in" : "out");
 
 		dep->endpoint.name = dep->name;
+		spin_lock_init(&dep->lock);
 
 		dwc3_trace(trace_dwc3_gadget, "initializing %s", dep->name);