vDPA/ifcvf: synchronize irqs in the reset routine

This commit synchronize irqs of the virtqueues
and config space in the reset routine.
Thus ifcvf_stop() and reset() are refactored as well.
This commit renames ifcvf_stop_hw() to ifcvf_stop()

Signed-off-by: Zhu Lingshan <lingshan.zhu@intel.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20230526145254.39537-5-lingshan.zhu@intel.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>