[compiler-rt] [builtins][NFC] Remove last usage of CRT_LDBL_128BIT (PR #68041)

[Alexander Richardson via llvm-commits]

https://github.com/arichardson commented:

I believe this is not quite right since it will break PPC64 where we will now use IEEE128 logbl, etc. unconditionally.

https://github.com/llvm/llvm-project/pull/68041