Move the functionality to retrieve the fw info into a dedicated device
type-agnostic function, hisi_sas_get_fw_info().

The reasoning is that this function will be required for future
pci-based platforms.

Also add some debug logs for failure.
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>