Revert: MEDIUM: evports: permit to report multiple events at once"

Revert: MEDIUM: evports: permit to report multiple events at once"

Tests have shown that switching nevlist to global.tune.maxpollevents
is totally unreliable when using evports, and that events seem to be
missed. A good reproducer seems to be QUIC. There are not enough
users of Solaris to warrant spending more time trying to get down to
this, and even the few that remain are by definition not interested
in performance, so let's just revert the commit that tried to lift the
value: e6662bf706 ("MEDIUM: evports: permit to report multiple events
at once").

No backport is needed.