[mlir][tosa] Fix tosa.transpose_conv2d decompositions for new version

The decomposition was no longer correct for transpose_conv2d to conv2d
after the updated TOSA specification. Specifically the behavior for
padding was changed to refer to padding the tranpsose_conv2d instead
of referencing the conv applied to the inverse transform.

Test was validated using the TOSA conformance tests.

Reviewed By: NatashaKnk

Differential Revision: https://reviews.llvm.org/D140503