UefiCpuPkg: Update return status to follow spec

SplitPage may return OUT_OF_RESOURCES if no memory resource to split
page entry. ConvertMemoryPageAttributes should also return
OUT_OF_RESOURCES instead of override the status to UNSUPPORTED.
Then EfiSetMemoryAttributes and EfiClearMemoryAttributes can return
correct status of OUT_OF_RESOURCES when requested attributes cannot
be applied due to lack of system resource.

Cc: Felix Polyudov <felixp@ami.com>
Cc: David Hsieh <davidhsieh@ami.com>
Cc: James Wang <jameswang@ami.com>
Signed-off-by: Crystal Lee <crystallee@ami.com>

UefiCpuPkg/CpuDxe/CpuPageTable.c

@@ -849,7 +849,6 @@ ConvertMemoryPageAttributes (
 
       Status = SplitPage (PageEntry, PageAttribute, SplitAttribute, AllocatePagesFunc);
       if (RETURN_ERROR (Status)) {
-        Status = RETURN_UNSUPPORTED;
         goto Done;
       }