scsi: hisi_sas: tidy host controller reset function a bit

scsi: hisi_sas: tidy host controller reset function a bit

BugLink: https://bugs.launchpad.net/bugs/1794166
This patch tidies host controller reset function by putting some code to
two new functions, and exports these two functions out, so that they could
be used by FLR feature to be realised.

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 4522204ab218a8c1f4d3901276deb0a61e7ac9c0)
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>