BaseTools: Add a keyword FvNameString in FDF

The keyword with value TRUE OR FALSE is used to
indicate whether the FV UI name is included in
FV EXT header as a entry or not.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Yingke Liu <yingke.d.liu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@18090 6f19259b-4bc3-4df7-8a09-765794883524