vdpa: add new callback get_vq_num_min in vdpa_config_ops

mainline inclusion
from mainline-v5.16-rc1
commit 3b970a58
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5WXCZ
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3b970a5842c9114c82e60744c84a7d06ee51b6f9



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This callback is optional. For vdpa devices that not support to change
virtqueue size, get_vq_num_min and get_vq_num_max will return the same
value, so that users can choose a correct value for that device.

Suggested-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Wu Zongyong <wuzongyong@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/f4af5b0abd660d9a29ab6b2f67bd6df10284a230.1635493219.git.wuzongyong@linux.alibaba.com


Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Pengyuan Zhao <zhaopengyuan@hisilicon.com>