Event megasas_io_read was added in commit e8f943c3, but never used.
Drop it.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-id: 1411476811-24251-3-git-send-email-armbru@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>