scsi: libsas: Move sas_get_ata_command_set() up to save the declaration

There is a sas_get_ata_command_set() declaration above sas_get_ata_info()
to make it compile. However, this function is defined in the same
file. Move it up to save the forward declaration.

Also remove the variable 'fis' which is not needed in this function.

Cc: John Garry <john.g.garry@oracle.com>
Signed-off-by: Jason Yan <yanaijie@huawei.com>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Reviewed-by: Jack Wang <jinpu.wang@ionos.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>