Correct the format of string table to support different variables for all SKU values of one HII PCD.

Reviewed-by: Zeng, Star <star.zeng@intel.com>
Reviewed-by: Feng, Bob C <bob.c.feng@intel.com>
Signed-off-by: Jiang Liu <jiang.a.liu@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2-buildtools/code/trunk/BaseTools@2633 c2973edb-eda0-4c78-bc6a-9341b269661f