Clean up DxeIpl:
1. Remove the assembly by using IoLib & BaseLib in MdePkg
2. Refine code to pass CYGWIN GCC tool chain build 

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@7404 6f19259b-4bc3-4df7-8a09-765794883524
14 files changed