[MPS] Fix conv1d backwards crash for channels last case (#85283)
Fixes pytorch#84511
Use the same logic as in the forward pass for the backward pass (in case of channels last, manually set the shape to NHWC)
Pull Request resolved: https://github.com/pytorch/pytorch/pull/85283
Approved by: https://github.com/malfet, https://github.com/razarmehr
