virtio_ring: put mapping error check in vring_map_one_sg

virtio_ring: put mapping error check in vring_map_one_sg

This patch put the dma addr error check in vring_map_one_sg().

The benefits of doing this:

1. reduce one judgment of vq->use_dma_api.
2. make vring_map_one_sg more simple, without calling
   vring_mapping_error to check the return value. simplifies subsequent
   code

Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20230810123057.43407-3-xuanzhuo@linux.alibaba.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>