Cost model: Add check for reverse shuffles to CostModel analysis

Check for reverse shuffles in the CostModel analysis pass and query
TargetTransform info accordingly. This allows us we can write test cases for
reverse shuffles.

radar://13171406

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174932 91177308-0d34-0410-b5e6-96231b3b80d8
ARM cost model: Add vector reverse shuffle costs

A reverse shuffle is lowered to a vrev and possibly a vext instruction (quad
word).

radar://13171406

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@174933 91177308-0d34-0410-b5e6-96231b3b80d8