BaseTools: Support TabSpace between section tag in DEC file

BaseTools: Support TabSpace between section tag in DEC file

Per DEC spec, multiple section tag use <TS> to separate, and it can
support Tab, so this patch fix the bug to use Tab.

<TabSpace> ::= {<Tab>} {<Space>}
<TS> ::= <TabSpace>*

Cc: Liming Gao <liming.gao@intel.com>
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Yanyan Zhang <yanyanx.zhang@intel.com>
Reviewed-by: Yonghong Zhu <yonghong.zhu@intel.com>