Add a GUIDed HOB to init Debug Print error level earlier in DXE. Add NULL PEIM librar...

Add a GUIDed HOB to init Debug Print error level earlier in DXE. Add NULL PEIM library to init HOB.

Debug Print Error level can be controled by an EFI variable. Update the DXE version of the library to use a HOB if the variable services are not yet availilbe. This allows the variable to be used early in the DXE phase.

approved-by: andrewfish
reviewed-by: lgao4

git-svn-id: https://edk2.svn.sourceforge.net/svnroot/edk2/trunk/edk2@12516 6f19259b-4bc3-4df7-8a09-765794883524