[MLIR] Fix affine.for unroll for multi-result upper bound maps

Fix affine.for unroll for multi-result upper bound maps: these can't be
unrolled/unroll-and-jammed in cases where the trip count isn't known to
be a multiple of the unroll factor.

Fix and clean up repeated/unnecessary checks/comments at helper callees.

Also, fix clang-tidy variable naming warnings and redundant includes.

Differential Revision: https://reviews.llvm.org/D114662