Fix incorrect invariant check in DAG Combine

Earlier this summer I fixed an issue where we were incorrectly combining
multiple loads that had different constraints such alignment, invariance,
temporality, etc. Apparently in one case I made copt paste error and swapped
alignment and invariance.

Tests included.

rdar://18816719

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220933 91177308-0d34-0410-b5e6-96231b3b80d8