scsi: pm80xx: Fix 'Unknown' max/min linkrate

scsi: pm80xx: Fix 'Unknown' max/min linkrate

Currently, the data flow of the max/min linkrate in the driver is

 * in pm8001_get_lrate_mode():
   hardcoded value ==> struct sas_phy

 * in pm8001_bytes_dmaed():
   struct pm8001_phy ==> struct sas_phy

 * in pm8001_phy_control():
   libsas data ==> struct pm8001_phy

Since pm8001_bytes_dmaed() follows pm8001_get_lrate_mode(), and the fields
in struct pm8001_phy are not initialized, sysfs
`/sys/class/sas_phy/phy-*/maximum_linkrate` always shows `Unknown`.

To fix the issue, change the dataflow to the following:

 * in pm8001_phy_init():
   initial value ==> struct pm8001_phy

 * in pm8001_get_lrate_mode():
   struct pm8001_phy ==> struct sas_phy

 * in pm8001_phy_control():
   libsas data ==> struct pm8001_phy

For negotiated linkrate, the current dataflow is:

 * in pm8001_get_lrate_mode():
   iomb data ==> struct asd_sas_phy ==> struct sas_phy

 * in pm8001_bytes_dmaed():
   struct asd_sas_phy ==> struct sas_phy

Since pm8001_bytes_dmaed() follows pm8001_get_lrate_mode(), the assignment
statements in pm8001_bytes_dmaed() are unnecessary and cleaned up.

Link: https://lore.kernel.org/r/20220707175210.528858-1-changyuanl@google.com
Reviewed-by: Igor Pylypiv <ipylypiv@google.com>
Acked-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Changyuan Lyu <changyuanl@google.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>