Revert "all: honour port for -monitor flash flag"

This reverts commit 7aac1a1391.

main.go

@@ -532,12 +532,7 @@ func Flash(pkgName, port string, options *compileopts.Options) error {
 		return fmt.Errorf("unknown flash method: %s", flashMethod)
 	}
 	if options.Monitor {
-		port, err := getDefaultPort(port, config.Target.SerialPort)
-		if err != nil {
-			return &commandError{"failed to locate port to monitor", port, err}
-		}
-
-		return Monitor(port, options)
+		return Monitor("", options)
 	}
 	return nil
 }