[llvm] [AMDGPU] Allow shinking instruction with dead sdst (PR #68028)

[Stanislav Mekhanoshin via llvm-commits]

rampitec wrote:

> For GFX, I quickly tried this on Navi21 shaders and saw no shift in _e32 versus _e64. But I might have missed something.

I am purely checking our lit tests.

https://github.com/llvm/llvm-project/pull/68028