virtio-net: unbreak vq resizing when coalescing is not negotiated

Don't break the resize action if the vq coalescing feature
named VIRTIO_NET_F_VQ_NOTF_COAL is not negotiated.

Fixes: f61fe5f0 ("virtio-net: fix the vq coalescing setting for vq resize")
Signed-off-by: Heng Qi <hengqi@linux.alibaba.com>
Reviewed-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: Eugenio Pé rez <eperezma@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>