Fix broken --filter-trace-xdp

It fails to run with --filter-trace-xdp:

```bash
2024/09/24 15:38:48 Attaching xdp progs...
2024/09/24 15:38:48 failed to trace XDP progs: failed to trace bpf progs: failed to load objects:
program fexit_xdp: attach Tracing/TraceFExit: fexit xdp not supported
```

Signed-off-by: Leon Hwang <[email protected]>

Author: Asphaltt

internal/pwru/tracing.go

@@ -189,11 +189,20 @@ func TraceXDP(coll *ebpf.Collection, spec *ebpf.CollectionSpec,
 	log.Printf("Attaching xdp progs...\n")
 
 	var t tracing
-	if err := t.trace(coll, spec, opts, outputSkb, outputShinfo, n2a, ebpf.XDP, "fentry_xdp"); err != nil {
-		log.Fatalf("failed to trace XDP progs: %v", err)
+	{
+		spec := spec.Copy()
+		delete(spec.Programs, "fexit_xdp")
+		if err := t.trace(coll, spec, opts, outputSkb, outputShinfo, n2a, ebpf.XDP, "fentry_xdp"); err != nil {
+			log.Fatalf("failed to trace XDP progs: %v", err)
+		}
 	}
-	if err := t.trace(coll, spec, opts, outputSkb, outputShinfo, n2a, ebpf.XDP, "fexit_xdp"); err != nil {
-		log.Fatalf("failed to trace XDP progs: %v", err)
+
+	{
+		spec := spec.Copy()
+		delete(spec.Programs, "fentry_xdp")
+		if err := t.trace(coll, spec, opts, outputSkb, outputShinfo, n2a, ebpf.XDP, "fexit_xdp"); err != nil {
+			log.Fatalf("failed to trace XDP progs: %v", err)
+		}
 	}
 
 	return &t