virtio_ring: switch to use dma_{map|unmap}_page()

virtio_ring: switch to use dma_{map|unmap}_page()

This patch switches to use dma_{map|unmap}_page() to reduce the
coverage of DMA operations. This would help for the following rework
on the virtio map operations.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20250821064641.5025-3-jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Lei Yang <leiyang@redhat.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>