[Hexagon] Fix TIR vrmpy tensorization

[masahi]

Hexagon tests using vrmpy tensorization were broken by the change in tir/tensor_intrin/hexagon.py from #12496. The change is a correct one from the TIR perspective, but it breaks tensorize pattern matching. Actually T.init() block is not necessary in a tensorize description, so just removing it fixes the breakage.

@mehrdadh

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• cc @Icemist, @mehrdadh _{See #10317 for details}
• Built docs for commit c38e15f can be found here.

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[junrushao]

Oh thanks for the update! In TIR, formally speaking, T.init() should only appear strictly under T.block(), so we got it removed to conform to the spec