ggml-webgpu: Fix vectorized handling in mul-mat and mul-mat-id (#22578)
* Fix vectorized condition of mul-mat-fast pipeline and add vectorized variant to mul-mat-id
* Apply suggestion from @CISC
Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>
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Co-authored-by: Sigbjørn Skjæret <sigbjorn.skjaeret@scala.com>