usb-tablet: fix serial compat property

s/kbd/tablet/, fixes cut+paste bug.

Cc: qemu-stable@nongnu.org
Reported-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Laurent Vivier <lvivier@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20190520081805.15019-1-kraxel@redhat.com

hw/core/machine.c

@@ -36,7 +36,7 @@ GlobalProperty hw_compat_3_1[] = {
     { "tpm-tis", "ppi", "false" },
     { "usb-kbd", "serial", "42" },
     { "usb-mouse", "serial", "42" },
-    { "usb-kbd", "serial", "42" },
+    { "usb-tablet", "serial", "42" },
     { "virtio-blk-device", "discard", "false" },
     { "virtio-blk-device", "write-zeroes", "false" },
 };