tools:checkdata: end checking if come to the end of table

End checking if come to the end of table.

Signed-off-by: Zhengwang Ruan <ruan.zhengwang@gmail.com>
tools:checkdata: add checking for the heads of the data table and file

1, Rename startChecking() to checkContent().
2, Add checkHead().

Signed-off-by: Zhengwang Ruan <ruan.zhengwang@gmail.com>