Revert "gdb_server,rtos: Differentiate rtos_get_gdb_reg failing and not implemented"

This reverts commit 15f3996.

Change-Id: I1002df6b2434b85025727c9583a20e83273e708e

Author: wangyanwen

src/server/gdb_server.c

@@ -1408,13 +1408,8 @@ static int gdb_get_register_packet(struct connection *connection,
 	LOG_DEBUG("-");
 #endif
 
-	if (target->rtos) {
-		retval = rtos_get_gdb_reg(connection, reg_num);
-		if (retval == ERROR_OK)
-			return ERROR_OK;
-		if (retval != ERROR_NOT_IMPLEMENTED)
-			return gdb_error(connection, retval);
-	}
+	if ((target->rtos) && (rtos_get_gdb_reg(connection, reg_num) == ERROR_OK))
+		return ERROR_OK;
 
 	retval = target_get_gdb_reg_list_noread(target, &reg_list, &reg_list_size,
 			REG_CLASS_ALL);