vdpa: set the virtqueue num during register

stable inclusion
from stable-v5.12
commit f00bdce0
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=f00bdce0455233a0b76dae6364442dca717a574c



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This patch delay the queue number setting to vDPA device
registering. This allows us to probe the virtqueue numbers between
device allocation and registering.

Reviewed-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Link: https://lore.kernel.org/r/20210223061905.422659-3-jasowang@redhat.com


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