remoteproc: virtio: set vdev status to reset after del vqs

Set the vdev status to reset (0) after shutdown the remoteproc
When remoteproc driver shutdown the remote, it copy the cached
table as the resource table, In the resource table, it has a field
to reflect the processor's status. During the shutdown, it didn't
mark the processor' status as reset after get copy the cached table,
and thus, this function is required to set the processor to reset
state.
Without this setting, there will be no issue to shutdown the
processor, but there will be warning Comes out from the virtio to say
the processor state is not under reset.

Signed-off-by: Wendy Liang <wendy.liang@xilinx.com>
Signed-off-by: Jason Wu <j.wu@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>