[llvm-branch-commits] [llvm] [AMDGPU] Make v2x64 BUILD_VECTOR legal on gfx1251 (PR #204470)

[Matt Arsenault via llvm-branch-commits]

https://github.com/arsenm approved this pull request.

LGTM as an incremental step, but this should be universal 

https://github.com/llvm/llvm-project/pull/204470