[llvm] [Mips] Fix wrong qNaN encoding when -mnan=legacy (PR #153777)

[via llvm-commits]

yingopq wrote:

> We should probably also consider making `-mnan=legacy` an error and stop pretending that we support it.

Now, based on your opinions and the issue, I agree with this approach: did not support and report an error.


https://github.com/llvm/llvm-project/pull/153777