[SCSI] isci: Fix IO fails when pull cable from phy in x4 wideport in MPC mode.

Failure seen pulling a cable from a x4 port configured in manual port
configuration (MPC) mode (MPC mode is set by the the OEM paramaters
provided by the platform or isci_firmware.bin).  While IO running to
devices behind and expander, plugging out the cable from phy is causing
IO failures and IO drops on disks and never recover.

It happens because during link up/down the phy were being taken out of
the port.

Fix: during link down the phy is kept in the same logical port.

Signed-off-by: Marcin Tomczak <marcin.tomczak@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>