Avoid creating 'load X, 0' instead of just 'load X'

Avoid creating 'load X, 0' instead of just 'load X'

This _trivial_ change causes GCSE and LICM to be much more effective at
hoisting loads.  Before it would not be able to eliminate 'load X' if there
was just a dominating 'load X, 0' because the expressions were not identical.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@3337 91177308-0d34-0410-b5e6-96231b3b80d8