Revert "Enable LoopLoadElimination by default"

This reverts commit r262250.

It causes SPEC2006/gcc to generate wrong result (166.s) in AArch64 when
running with *ref* data set.  The error happens with
"-Ofast -flto -fuse-ld=gold" or "-O3 -fno-strict-aliasing".

llvm-svn: 262839