[SPARK-6574] [PySpark] fix sql example

Fix the import in sql example.

Author: Davies Liu <davies@databricks.com>

Closes #5230 from davies/fix_sql_example and squashes the following commits:

7ecc5f4 [Davies Liu] fix sql example

examples/src/main/python/sql.py

@@ -19,7 +19,7 @@ import os
 
 from pyspark import SparkContext
 from pyspark.sql import SQLContext
-from pyspark.sql import Row, StructField, StructType, StringType, IntegerType
+from pyspark.sql.types import Row, StructField, StructType, StringType, IntegerType
 
 
 if __name__ == "__main__":