cciss: Handle special case for sysfs attributes of the first logical drive.

For c0dx where x is not 0, we handle deletion and addition simply,
but for c0d0, there is the special case that even when there's no
disk, the device node exists so that the controller may be accessed.
So, for c0d0, we only create the sysfs entries once, when a controller
is added, and only remove them once, when a controller is being
taken down.

Signed-off-by: Stephen M. Cameron <scameron@beardog.cce.hp.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>