[MLIR] Fix affine analysis methods for affine.parallel

Drop unnecessary bailout in checkMemRefAccessDependence in the presence of
surrounding affine.parallel ops. When the affine.parallel op was added, affine
analysis methods weren't extended to account for it. Fix this and allow memref
dependence check to work in the presence of affine.parallel ops in the mix.

Rename isForInductionVar -> isAffineForInductionVar, getLoopIVs ->
getAffineForIVs to avoid confusion since that's what they were.

Differential Revision: https://reviews.llvm.org/D141254