Remove a processFixupValue hack.
The intention of processFixupValue is not to redefine the semantics of
MCExpr. It is odd enough that a expression lowers to a PCRel MCExpr or
not depending on what it looks like. At least it is a local hack now.
I left a fix for anyone trying to figure out what producers should be
producing a different expression.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@306200 91177308-0d34-0410-b5e6-96231b3b80d8