[llvm] [AMDGPU] Add gfx1251 V_PK_ADD/SUB_NC_U64 (PR #203607)

[Stanislav Mekhanoshin via llvm-commits]

rampitec wrote:

* #203607 👈
* `main`

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This stack of pull requests is managed by <a href="https://github.com/shiltian/sgh"><b>sgh</b></a>.
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https://github.com/llvm/llvm-project/pull/203607