Use MemorySSA in LICM to do sinking and hoisting.

Summary:
Step 2 in using MemorySSA in LICM:
Use MemorySSA in LICM to do sinking and hoisting, all under "EnableMSSALoopDependency" flag.
Promotion is disabled.

Enable flag in LICM sink/hoist tests to test correctness of this change. Moved one test which
relied on promotion, in order to test all sinking tests.

Reviewers: sanjoy, davide, gberry, george.burgess.iv

Subscribers: llvm-commits, Prazek

Differential Revision: https://reviews.llvm.org/D40375

llvm-svn: 350879