input: activate legacy kbd

Restores traditional behavior:  Keyboard input will be routed to the most
recently added keyboard.  Without this all kbd input goes to the ps/2
keyboard, even if you add a usb keyboard to your guest.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

ui/input-legacy.c

@@ -333,6 +333,7 @@ QEMUPutKbdEntry *qemu_add_kbd_event_handler(QEMUPutKBDEvent *func, void *opaque)
     entry->opaque = opaque;
     entry->s = qemu_input_handler_register((DeviceState *)entry,
                                            &legacy_kbd_handler);
+    qemu_input_handler_activate(entry->s);
     return entry;
 }