Move sg structure off stack and into virtnet_info structure.
This helps remove extra sg_init_table calls as well as reduce
stack usage.
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>