Fix MKLDNN conv2d 5d weight handling (#34115)
Summary:
Effectively backporting https://github.com/pytorch/pytorch/pull/32422/commits/c5c00c119fd2631e8500747a04ea2ca9c9933741 before that PR lands
The bug didn't manifesting itself earlier because MkldnnConv2d constructor didn't reorder the weights. So the issue was arising only on second serialization/deserialization. This also fixes the constructor to deliver better perf right away.
Note, that I still serialize 5d tensor - it was the previous behavior, we have to handle it anyway and with https://github.com/pytorch/pytorch/issues/32422 the output of `mkldnn_reorder_conv2d_weight` will always be 4d.
cc pinzhenx
Pull Request resolved: https://github.com/pytorch/pytorch/pull/34115
Reviewed By: wanchaol
Differential Revision: D20224685
Pulled By: dzhulgakov
fbshipit-source-id: 24ca9227c4eb4c139096a64ae348808d7478d7dc
