[SPARK-14981][SQL] Throws exception if DESC is specified for sorting columns

## What changes were proposed in this pull request?

Currently Spark SQL doesn't support sorting columns in descending order. However, the parser accepts the syntax and silently drops sorting directions. This PR fixes this by throwing an exception if `DESC` is specified as sorting direction of a sorting column.

## How was this patch tested?

A test case is added to test the invalid sorting order by checking exception message.

Author: Cheng Lian <lian@databricks.com>

Closes #12759 from liancheng/spark-14981.