[LoopInterchange] Add more debug messages to currentLimitations(). 
[LoopInterchange] Add more debug messages to currentLimitations(). 

Summary: This makes it easier to find out which limitation prevented this pass from doing its work.

Reviewers: karthikthecool, mzolotukhin, efriedma, mcrosier

Reviewed By: mcrosier

Subscribers: mcrosier, llvm-commits

Differential Revision: https://reviews.llvm.org/D34940

git-svn-id: 0ff597fd157e6f4fc38580e8d64ab130330d2411@307035 91177308-0d34-0410-b5e6-96231b3b80d8

GPUOpen-Drivers/llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,apple/swift-llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,apple/swift-llvm,llvm-mirror/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,GPUOpen-Drivers/llvm,GPUOpen-Drivers/llvm,llvm-mirror/llvm,apple/swift-llvm,apple/swift-llvm