[SCSI] isci: The port state should be set to stopping on the last phy.

Fixes a bug where any phy removed from the port set the port
state to "stopping" - do this only when the last phy removed
from the port.

Signed-off-by: Jeff Skirvin <jeffrey.d.skirvin@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>