1. Add ISCSI iBFT CHAP types to IScsiBootFirmwareTable.h.
2. Fix ISCSI iBFT's CHAP type mismatch bug caused by 14918.

Signed-off-by: Fu Siyuan <siyuan.fu@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>
Reviewed-by: Dong, Guo <guo.dong@intel.com>

git-svn-id: svn://svn.code.sf.net/p/edk2/code/trunk/edk2/MdePkg@14953 6f19259b-4bc3-4df7-8a09-765794883524