enum sas_class prob would have been useful if function sas_show_class() was
ever implemented, which it wasn't.

enum sas_class is used as asd_sas_port.class and asd_sas_phy.class, which
are only ever set, so delete these members and the enum.
Signed-off-by: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20230815115156.343535-3-john.g.garry@oracle.comReviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>