Add early exit on reassociation of 0 expression.

Summary:

Before the patch a try to reassociate ((v * 16) * 0) * 1 fall into infinite loop

Reviewers: pankajchawla

Differential Revision: http://reviews.llvm.org/D41467

From: Evgeny Stupachenko <evstupac@gmail.com>
                         <evgeny.v.stupachenko@intel.com>
llvm-svn: 326861