[mlir][affine] Normalize constant valued bound loop

This change aims to resolve the issue reported in https://github.com/llvm/llvm-project/issues/59994.

After calling AffineForOp#setUpperBound and setLowerBound, it makes the original affine map structure inconsistent. It's necessary to keep the original map to build the new induction vars.

Reviewed By: bondhugula

Differential Revision: https://reviews.llvm.org/D142082