spice: do not require TCP ports

It is possible to use Spice server without TCP port.  On local VM,
qemu (and libvirt) can add new clients thanks to QMP add_client command.
Signed-off-by: NMarc-André Lureau <marcandre.lureau@gmail.com>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

ui/spice-core.c

@@ -661,10 +661,6 @@ void qemu_spice_init(void)
     }
     port = qemu_opt_get_number(opts, "port", 0);
     tls_port = qemu_opt_get_number(opts, "tls-port", 0);
-    if (!port && !tls_port) {
-        error_report("neither port nor tls-port specified for spice");
-        exit(1);
-    }
     if (port < 0 || port > 65535) {
         error_report("spice port is out of range");
         exit(1);