add comments to note why EFI_MISC_PORT_DEVICE_PATH and etc exists here , which is not defined in MiscSubclass spec.

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@8797 6f19259b-4bc3-4df7-8a09-765794883524
1 file changed