USB: xhci: unsigned char never equals -1

There were some places that compared port_speed == -1 where port_speed
is a u8.  This doesn't work unless we cast the -1 to u8.  Some places
did it correctly.

Instead of using -1 directly, I've created a DUPLICATE_ENTRY define
which does the cast and is more descriptive as well.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>
diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index cfc1ad9..c6d1462 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -1209,7 +1209,7 @@
 		 * Skip ports that don't have known speeds, or have duplicate
 		 * Extended Capabilities port speed entries.
 		 */
-		if (port_speed == 0 || port_speed == -1)
+		if (port_speed == 0 || port_speed == DUPLICATE_ENTRY)
 			continue;
 
 		/*
@@ -1260,7 +1260,7 @@
 				port_id);
 		goto cleanup;
 	}
-	if (major_revision == (u8) -1) {
+	if (major_revision == DUPLICATE_ENTRY) {
 		xhci_warn(xhci, "Event for port %u duplicated in"
 				"Extended Capabilities, ignoring.\n",
 				port_id);