Revert "core: reactor: fix a typo in `smp_pollfn::poll()`"
Revert "core: reactor: fix a typo in `smp_pollfn::poll()`"

This reverts commit c41c30b9cad2f907bc82875e1c2b78223556a789.

The unobvious difference is that a() | b() will call _both_ a()
and b() even if a() returns true. The a() || b() can leave b()
uncalled. As far as this particular patch is concerned -- in case
smp messages were polled alien messages would start starving after
that patch.

avikivity/seastar,syuu1228/seastar,avikivity/seastar,syuu1228/seastar,scylladb/seastar,syuu1228/seastar,scylladb/seastar,scylladb/seastar,avikivity/seastar