vdpa: min vq num of vdpa device cannot be greater than max vq num

Just failed to probe the vdpa device if the min virtqueue num returned
by get_vq_num_min is greater than the max virtqueue num returned by
get_vq_num_max.

Signed-off-by: Wu Zongyong <wuzongyong@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/21199b62cc10b2a9f2cf90eeb63ad080645d881f.1635493219.git.wuzongyong@linux.alibaba.com


Signed-off-by: Michael S. Tsirkin <mst@redhat.com>