scsi: core: Modify the scsi_send_eh_cmnd() return value for the SDEV_BLOCK case

The comment above scsi_send_eh_cmnd() says: "Returns SUCCESS or FAILED or
NEEDS_RETRY". This patch makes all values returned by scsi_send_eh_cmnd()
match the documentation of this function. This change does not affect the
behavior of scsi_eh_tur() nor of scsi_eh_try_stu() nor of the
scsi_request_sense() callers.

See also commit bbe9fb0d04b9 ("scsi: Avoid that .queuecommand() gets called
for a blocked SCSI device"; v5.3).

Link: https://lore.kernel.org/r/20210415220826.29438-5-bvanassche@acm.org
Cc: Christoph Hellwig <hch@lst.de>
Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Daniel Wagner <dwagner@suse.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>