Remove the "WantsWholeFile" concept, as it's no longer needed. CBE

Remove the "WantsWholeFile" concept, as it's no longer needed. CBE
and the others use the regular addPassesToEmitFile hook now, and
llc no longer needs a bunch of redundant code to handle the
whole-file case.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@103492 91177308-0d34-0410-b5e6-96231b3b80d8