Enable warningif opcode in browser.

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/MdePkg@14624 6f19259b-4bc3-4df7-8a09-765794883524