[clang] [CIR][AMDGPU] Add support for AMDGCN frexp_mant builtins (PR #198121)

[Ayokunle Amodu via cfe-commits]

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ayokunle321 wrote:

It matches the test name now. Could always consolidate them if we do decide to go ahead in that direction.

https://github.com/llvm/llvm-project/pull/198121