[MLIR] Add division normalization by GCD in `getDivRepr` fn.

This commits adds division normalization in  the `getDivRepr` function which extracts
 the gcd from the dividend and divisor and normalizes them.

Signed-off-by: Prashant Kumar <pk5561@gmail.com>

Reviewed By: bondhugula

Differential Revision: https://reviews.llvm.org/D115595