scsi: core: Fixup calling convention for scsi_mode_sense()

The description for scsi_mode_sense() claims to return the number of valid
bytes on success, which is not what the code does.  Additionally there is
no gain in returning the SCSI status, as everything the callers do is to
check against scsi_result_is_good(), which is what scsi_mode_sense() does
already.  So change the calling convention to return a standard error code
on failure, and 0 on success, and adapt the description and all callers.

Link: https://lore.kernel.org/r/20210427083046.31620-4-hare@suse.de


Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>