vdpa: support exposing the count of vqs to userspace

stable inclusion
from stable-v5.18
commit b04d910a
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I5WXCZ
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b04d910af330b55e1d5d6eb9ecd53a375a9cf81c



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- GET_VQS_COUNT: the count of virtqueues that exposed

Signed-off-by: Longpeng <longpeng2@huawei.com>
Link: https://lore.kernel.org/r/20220315032553.455-4-longpeng2@huawei.com


Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Longpeng &amp;lt;&lt;a href="mailto:longpeng2@huawei.com" <target="_blank"&gt;longpeng2@huawei.com&lt;/a&gt;&amp;gt;&lt;br>
Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Pengyuan Zhao <zhaopengyuan@hisilicon.com>