Fix the following gcc warning:
drivers/vhost/vdpa.c:299:5: warning: variable 'status' set but not used [-Wunused-but-set-variable]
  u8 status;
     ^~~~~~
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Link: https://lore.kernel.org/r/20200402065106.20108-1-yanaijie@huawei.comSigned-off-by: Michael S. Tsirkin <mst@redhat.com>