unix: use relaxed loads/stores for clock id
unix: use relaxed loads/stores for clock id

This was part of commit c70dd705 ("unix: use relaxed loads/stores for
feature checks") and was reviewed as such but I accidentally dropped
it in the rebase before the final merge.

Fixes: https://github.com/libuv/libuv/issues/2884
PR-URL: https://github.com/libuv/libuv/pull/2886
Reviewed-By: Anna Henningsen <2bc1ecb410e142bce83bce6f212b41e1781536dc@addaleax.net>
Reviewed-By: Jameson Nash <99e7f19e9f64df56d4e81dc00b8566e722cdd766@gmail.com>

unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso,unknownbrackets/maxcso