Update comments for HiiConfigRoutine->ExtractConfig function, also update HiiConfigRoutine->ConfigToBlock/BlockToConfig to follow this new spec.

Signed-off-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/MdeModulePkg@14593 6f19259b-4bc3-4df7-8a09-765794883524
Add some comments, clear describe the efi varstore type.

Signed-off-by: Eric Dong <eric.dong@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>

git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/MdeModulePkg@14594 6f19259b-4bc3-4df7-8a09-765794883524