cuda : use SIMT implicit GEMM conv2d on AMD without WMMA (#30325)
* cuda : use SIMT implicit GEMM conv2d on AMD without WMMA
Assisted-by: Claude Opus
* cuda : update conv2d SIMT comment
* cuda : skip SIMT conv2d on AMD for short reductions
Co-authored-by: thelittlefireman <5165783+thelittlefireman@users.noreply.github.com>
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Co-authored-by: thelittlefireman <5165783+thelittlefireman@users.noreply.github.com>