usb: dwc3: add count field to event buffer

we can cache the last read value of the event
buffer count register on this field, for later
handling.
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc3/core.h

@@ -370,6 +370,7 @@ struct dwc3_trb;
  * @buf: _THE_ buffer
  * @length: size of this buffer
  * @lpos: event offset
+ * @count: cache of last read event count register
  * @flags: flags related to this event buffer
  * @dma: dma_addr_t
  * @dwc: pointer to DWC controller
@@ -378,6 +379,7 @@ struct dwc3_event_buffer {
 	void			*buf;
 	unsigned		length;
 	unsigned int		lpos;
+	unsigned int		count;
 	unsigned int		flags;
 
 #define DWC3_EVENT_PENDING	BIT(0)