ide: core: add cleanup function

As the pci ahci can be hotplug and unplug, in the ahci unrealize
function it should free all the resource once allocated in the
realized function. This patch add ide_exit to free the resource.

Signed-off-by: Li Qiang <liqiang6-s@360.cn>
Message-id: 1488449293-80280-3-git-send-email-liqiang6-s@360.cn
Signed-off-by: John Snow <jsnow@redhat.com>