vdpa_sim: add work_fn in vdpasim_dev_attr

stable inclusion
from stable-v5.11
commit a13b5918
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=a13b5918fdd0dd7987aa5f3c202f68ed6ad468bb



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Rename vdpasim_work() in vdpasim_net_work() and add it to
the vdpasim_dev_attr structure.

Co-developed-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://lore.kernel.org/r/20201215144256.155342-10-sgarzare@redhat.com


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