vsock/virtio: use skb_frag_*() helpers

Minor fix for virtio: code wanting to access the fields inside an skb
frag should use the skb_frag_*() helpers, instead of accessing the
fields directly. This allows for extensions where the underlying
memory is not a page.
Acked-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: Mina Almasry <almasrymina@google.com>
Link: https://lore.kernel.org/r/20240102205905.793738-1-almasrymina@google.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/vmw_vsock/virtio_transport.c

@@ -153,10 +153,10 @@ virtio_transport_send_pkt_work(struct work_struct *work)
 				 * 'virt_to_phys()' later to fill the buffer descriptor.
 				 * We don't touch memory at "virtual" address of this page.
 				 */
-				va = page_to_virt(skb_frag->bv_page);
+				va = page_to_virt(skb_frag_page(skb_frag));
 				sg_init_one(sgs[out_sg],
-					    va + skb_frag->bv_offset,
-					    skb_frag->bv_len);
+					    va + skb_frag_off(skb_frag),
+					    skb_frag_size(skb_frag));
 				out_sg++;
 			}
 		}