[PATCH] libata: fix ata_port_detach() for old EH ports

ata_prot_detach() did nothing for old EH ports and thus SCSI hosts
associated with those ports are left dangling after they are detached
leaving stale devices and causing oops eventually.  Make
ata_port_detach() remove SCSI hosts for old EH ports.

Signed-off-by: Tejun Heo <htejun@gmail.com>