[cublas][cublasLt] Fall back to unfused `addmm` for 2-byte-aligned inputs (#92201)
Fix for this issue surfaced from the discuss forum: https://discuss.pytorch.org/t/cuda-error-cublas-status-not-supported-when-calling-cublasltmatmul-from-torch-nn-functional-linear/170214
Note that PyTorch builds before #71200 should not be affected as there was no `cublasLt` dispatch path. Additionally, the provided repro has the quirk of using a 3D input, which means it will not dispatch to `cublasLt`-backed `addmm` until builds that include #72728. Changing the input to 2D by trivially removing the size `1` dimension will surface the failure on builds after #71200.
Interestingly, the use-case where _all_ inputs are 2-byte aligned are supported (runs without crashing), but when some are > 2-byte and some are == 2-byte are not. This behavior suggests that the `cuBlastLt` heuristics are incorrect, as the heuristic function has visibility of the raw pointer values via the descriptors when it is called.
We will follow up with `cuBlasLt` but this fix is needed to prevent unnecessary crashes for now.
CC @ptrblck @ngimel
Pull Request resolved: https://github.com/pytorch/pytorch/pull/92201
Approved by: https://github.com/ngimel
