virtio-console: Use exitfn for virtserialport, too

virtio-console: Use exitfn for virtserialport, too

virtconsole and virtserialport are identical in every other aspect
except for the distinguishing VirtIOSerialPortClass::is_console field.

Cc: qemu-stable@nongnu.org
Signed-off-by: Andreas Färber <afaerber@suse.de>
Signed-off-by: Andreas Färber <afaerber@suse.de>
Message-id: 1375313326-14966-1-git-send-email-afaerber@suse.de
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
(cherry picked from commit 203439ce0a832e36b276f10892846bd91ee836eb)

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>