[compiler-rt] [builtins] Fix logb / logbl tests

Like was done before in D67999 for `logbf`, this patch fixes the tests for
the internal compiler-rt implementations of `logb` and `logbl` to consider
all NaNs equivalent. Not doing so was resulting in test failures for
riscv64, since the the NaNs had different signs, but the spec doesn't
specify the NaN signedness or payload.

Fixes bug 44244.

Reviewers: rupprecht, delcypher
Reviewed By: rupprecht, delcypher
Differential Revision: https://reviews.llvm.org/D74826