[MLIR] Simplify affine.if ops with trivial conditions

The commit simplifies affine.if ops :
The affine if operation gets removed if the condition is universally true or false and then/else block is merged with the parent block.

Signed-off-by: Shashij Gupta <shashij.gupta@polymagelabs.com>

Reviewed By: bondhugula, pr4tgpt

Differential Revision: https://reviews.llvm.org/D104015