scsi: core: Show SCMD_LAST in text form

The SCSI debugfs code supports showing information about pending commands,
including translating SCSI command flags from numeric into text format.
Also convert the SCMD_LAST flag from numeric into text form.

Link: https://lore.kernel.org/r/20211129194609.3466071-4-bvanassche@acm.org
Fixes: 8930a6c2

 ("scsi: core: add support for request batching")
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>