retire ERROR_INVALID_ARGUMENTS and replace with ERROR_COMMAND_SYNTAX_ERROR

Change-Id: I6dee51e1fab1944085391f274a343cdb9014c7a4
Signed-off-by: Øyvind Harboe <oyvind.harboe@zylin.com>
Reviewed-on: http://openocd.zylin.com/300
Tested-by: jenkins
Reviewed-by: Øyvind Harboe <oyvindharboe@gmail.com>
Reviewed-by: Spencer Oliver <spen@spen-soft.co.uk>

src/server/server.c

@@ -657,7 +657,7 @@ SERVER_PORT_COMMAND()
 		break;
 	}
 	default:
-		return ERROR_INVALID_ARGUMENTS;
+		return ERROR_COMMAND_SYNTAX_ERROR;
 	}
 	return ERROR_OK;
 }
@@ -676,7 +676,7 @@ SERVER_PIPE_COMMAND()
 		break;
 	}
 	default:
-		return ERROR_INVALID_ARGUMENTS;
+		return ERROR_COMMAND_SYNTAX_ERROR;
 	}
 	return ERROR_OK;
 }