add Dhcp6/Mtftp6/Udp6 three protocol's definitions into MdePkg to comply with UEFI2.3 spec.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@9087 6f19259b-4bc3-4df7-8a09-765794883524
3 files changed