In preparation to enabling -Wimplicit-fallthrough, mark switch cases
where we are expecting to fall through.
Addresses-Coverity-ID: 
1402059 ("Missing break in switch")
Addresses-Coverity-ID: 
1402060 ("Missing break in switch")
Addresses-Coverity-ID: 
1402061 ("Missing break in switch")
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
                        goto xdp_xmit;
                default:
                        bpf_warn_invalid_xdp_action(act);
+                       /* fall through */
                case XDP_ABORTED:
                        trace_xdp_exception(vi->dev, xdp_prog, act);
                case XDP_DROP:
                        goto xdp_xmit;
                default:
                        bpf_warn_invalid_xdp_action(act);
+                       /* fall through */
                case XDP_ABORTED:
                        trace_xdp_exception(vi->dev, xdp_prog, act);
+                       /* fall through */
                case XDP_DROP:
                        if (unlikely(xdp_page != page))
                                __free_pages(xdp_page, 0);