Revert r174343, "When the target-independent DAGCombiner inferred a higher alignment for a load,"

It caused hangups in compiling clang/lib/Parse/ParseDecl.cpp and clang/lib/Driver/Tools.cpp in stage2 on some hosts.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174374 91177308-0d34-0410-b5e6-96231b3b80d8