usb: dwc3: core: avoid Overflow events

Now that we're handling so many transfers at a time
and for some dwc3 revisions LPM events *must* be
enabled, we can fall into a situation where too many
events fire and we start receiving Overflow events.

Let's do what XHCI does and allocate a full page for
the Event Ring, this will avoid any future issues.

Cc: <stable@vger.kernel.org> # v4.9
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>

drivers/usb/dwc3/core.h

@@ -45,9 +45,7 @@
 #define DWC3_XHCI_RESOURCES_NUM	2
 
 #define DWC3_SCRATCHBUF_SIZE	4096	/* each buffer is assumed to be 4KiB */
-#define DWC3_EVENT_SIZE		4	/* bytes */
-#define DWC3_EVENT_MAX_NUM	64	/* 2 events/endpoint */
-#define DWC3_EVENT_BUFFERS_SIZE	(DWC3_EVENT_SIZE * DWC3_EVENT_MAX_NUM)
+#define DWC3_EVENT_BUFFERS_SIZE	4096
 #define DWC3_EVENT_TYPE_MASK	0xfe
 
 #define DWC3_EVENT_TYPE_DEV	0