scsi: hisi_sas: fix the issue of setting linkrate register

scsi: hisi_sas: fix the issue of setting linkrate register

BugLink: https://bugs.launchpad.net/bugs/1768974
It is not right to set the register PROG_PHY_LINK_RATE while PHY is still
enabled. So if we want to change PHY linkrate, we need to disable PHY before
setting the register PROG_PHY_LINK_RATE, and then start-up PHY. This patch
is to fix this issue.

Signed-off-by: Xiaofei Tan <tanxiaofei@huawei.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
(cherry picked from commit 0006ce29e87ba357f64ee73e92c8aefc270fd315)
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>