Only MS IntelliMouse have a Z axis, prevent a false positive triggered by -Wuninitialized reported by jsg@.
Only MS IntelliMouse have a Z axis, prevent a false positive triggered
by -Wuninitialized reported by jsg@.

ok stsp@

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars