libata: move ata_dev_disable() to libata-eh.c

ata_dev_disable() is about to be more tightly integrated into EH
logic.  Move it to libata-eh.c.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>
3 files changed