[llvm] [AMDGPU] Replace zext pattern from reg_sequence to cvt_u32_u16 (PR #208045)

[Joe Nash via llvm-commits]

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

LGTM on the grounds it is a temporary workaround for a compile time issue and we will reintroduce the patterns when the root cause can be fixed

https://github.com/llvm/llvm-project/pull/208045