move multiaddr protocol definitions to go-multiaddr

That way, users don't need to import the transport just to parse a websocket
multiaddr.

p2p/transport/websocket/websocket.go

@@ -3,7 +3,6 @@ package websocket
 
 import (
 	"context"
-	"fmt"
 	"net"
 	"net/http"
 	"net/url"
@@ -20,11 +19,9 @@ import (
 )
 
 // WsProtocol is the multiaddr protocol definition for this transport.
-var WsProtocol = ma.Protocol{
-	Code:  477,
-	Name:  "ws",
-	VCode: ma.CodeToVarint(477),
-}
+//
+// Deprecated: use `ma.ProtocolWithCode(ma.P_WS)
+var WsProtocol = ma.ProtocolWithCode(ma.P_WS)
 
 // WsFmt is multiaddr formatter for WsProtocol
 var WsFmt = mafmt.And(mafmt.TCP, mafmt.Base(WsProtocol.Code))
@@ -46,11 +43,6 @@ var upgrader = ws.Upgrader{
 }
 
 func init() {
-	err := ma.AddProtocol(WsProtocol)
-	if err != nil {
-		panic(fmt.Errorf("error registering websocket protocol: %s", err))
-	}
-
 	manet.RegisterNetCodec(WsCodec)
 }