scsi: do not decode sense extras

Currently we're only decoding sense extras for tape devices.
And even there only for fixed format sense formats.
As this is of rather limited use in the general case we should
be stop trying to decode sense extras; the tape driver does
its own decoding anyway.

Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Robert Elliott <elliott@hp.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>