virtio-input: fix emulated tablet axis ranges

The reported maximum was wrong. The X and Y coordinates are 0-based
so if size is 8000 maximum must be 7FFF.

Signed-off-by: Ladi Prosek <lprosek@redhat.com>
Message-id: 1460128893-10244-1-git-send-email-lprosek@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

hw/input/virtio-input-hid.c

@@ -484,12 +484,12 @@ static struct virtio_input_config virtio_tablet_config[] = {
         .select    = VIRTIO_INPUT_CFG_ABS_INFO,
         .subsel    = ABS_X,
         .size      = sizeof(virtio_input_absinfo),
-        .u.abs.max = const_le32(INPUT_EVENT_ABS_SIZE),
+        .u.abs.max = const_le32(INPUT_EVENT_ABS_SIZE - 1),
     },{
         .select    = VIRTIO_INPUT_CFG_ABS_INFO,
         .subsel    = ABS_Y,
         .size      = sizeof(virtio_input_absinfo),
-        .u.abs.max = const_le32(INPUT_EVENT_ABS_SIZE),
+        .u.abs.max = const_le32(INPUT_EVENT_ABS_SIZE - 1),
     },
     { /* end of list */ },
 };