scsi: hisi_sas: Reject setting programmed minimum linkrate > 1.5G

The SAS controller cannot support a programmed minimum linkrate of > 1.5G
(it will always negotiate to 1.5G at least), so just reject it.

This solves a strange situation where the PHY negotiated linkrate may be
less than the programmed minimum linkrate.

Signed-off-by: Luo Jiaxing <luojiaxing@huawei.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>