zink: fix typo that's definitely not at all embarrassing or anything like that
requested to merge zmike/mesa:zink-totally_normal_patch_thats_mostly_formatting_and_barely_even_any_functional_changes_or_bug_fixes_haha_so_trivial into main
and also adjust some formatting to pad out the diff and really make sure nobody notices that anything was ever amiss here
Fixes: 787412b7 ("zink: break out region overlap testing function into helper")