[Unity][DLight] Use less shared memory for gemv

[Hzfengsy]

This PR fixes the issue of the GEMV rule uses too much shared memory on llama-70B model.

May have perf regression w/o #15471. (Actually not sure)

cc @cyx-6

[tvm-bot]

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• cc @quic-sanirudh _{See #10317 for details}

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