scsi: mpi3mr: Use negotiated link rate from DevicePage0

scsi: mpi3mr: Use negotiated link rate from DevicePage0

Firmware populates the negotiated SAS link rate in DevicePage0 during
device discovery. Update mpi3mr to cache this value while initializing
the target device.

When available, the cached link rate is used instead of issuing
additional SAS PHY or expander PHY page reads.  If the DevicePage0 value
is missing or invalid, the driver falls back to the existing PHY-based
mechanism.

Signed-off-by: Ranjan Kumar <ranjan.kumar@broadcom.com>
Link: https://patch.msgid.link/20260116060719.32937-5-ranjan.kumar@broadcom.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>