[llvm] [NVPTX] Support llvm.{exp2, log2} for f32 and vector of f32 (PR #120519)

[Princeton Ferro via llvm-commits]

Prince781 wrote:

Okay, this feature is now behind the flags `-nvptx-approx-exp2f32` and `-nvptx-approx-log2f32`, which are off by default.

https://github.com/llvm/llvm-project/pull/120519