sas_sata_ops uses ata_std_postreset as .postreset callback. However,
ata_std_postreset() calls sata_scr_read()/sata_scr_write() which need to
access the ATA SCR register. This register not available in the libsas case
and the functions always return -EOPNOTSUPP.

Drop the .postreset callback.

Link: https://lore.kernel.org/r/1595408643-63011-2-git-send-email-luojiaxing@huawei.comReviewed-by: John Garry <john.garry@huawei.com>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Luo Jiaxing <luojiaxing@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>