The lifetime of the timer is well-known (it cannot outlive
qemu_co_sleep_ns_wakeable, because it's deleted by the time the
coroutine resumes), so it is not necessary to place it on the heap.

Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 20210517100548.28806-2-pbonzini@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>