ohci: don't die on ED_LINK_LIMIT overflow

Stop processing the descriptor list instead. The next frame timer tick will
resume the work

Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1686705
Suggested-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
Message-id: 20190321085212.10796-1-lvivier@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

hw/usb/hcd-ohci.c

@@ -1200,7 +1200,7 @@ static int ohci_service_ed_list(OHCIState *ohci, uint32_t head, int completion)
     if (head == 0)
         return 0;
 
-    for (cur = head; cur; cur = next_ed) {
+    for (cur = head; cur && link_cnt++ < ED_LINK_LIMIT; cur = next_ed) {
         if (ohci_read_ed(ohci, cur, &ed)) {
             trace_usb_ohci_ed_read_error(cur);
             ohci_die(ohci);
@@ -1209,11 +1209,6 @@ static int ohci_service_ed_list(OHCIState *ohci, uint32_t head, int completion)
 
         next_ed = ed.next & OHCI_DPTR_MASK;
 
-        if (++link_cnt > ED_LINK_LIMIT) {
-            ohci_die(ohci);
-            return 0;
-        }
-
         if ((ed.head & OHCI_ED_H) || (ed.flags & OHCI_ED_K)) {
             uint32_t addr;
             /* Cancel pending packets for ED that have been paused.  */