[llvm] [AMDGPU] Fix LDS allocation granularity in occupancy computation for RDNA 2 (PR #219495)

[Shilei Tian via llvm-commits]

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shiltian wrote:

@chinmaydd already has a PR up somewhere IIRC, and yes, we need to apply the same fix there.

https://github.com/llvm/llvm-project/pull/219495