scsi: Show .retries and .jiffies_at_alloc in debugfs

Make these two member variables available in debugfs such that their
value can be verified by kernel developers. An example of the new
output:

ffff8804a513d480 {.op=READ, .cmd_flags=META|PRIO, .rq_flags=MQ_INFLIGHT|DONTPREP|IO_STAT|STATS, .atomic_flags=STARTED, .tag=17, .internal_tag=-1, .cmd=Read(10) 28 00 08 81 32 38 00 00 08 00, .retries=0, allocated 0.010 s ago}

Signed-off-by: Bart Van Assche <[e-mail]>
Cc: Hannes Reinecke <[e-mail]>
Cc: Christoph Hellwig <[e-mail]>
Cc: Johannes Thumshirn <[e-mail]>
Reviewed-by: Johannes Thumshirn <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/scsi/scsi_debugfs.c

···
 void scsi_show_rq(struct seq_file *m, struct request *rq)
 {
 	struct scsi_cmnd *cmd = container_of(scsi_req(rq), typeof(*cmd), req);
+	int msecs = jiffies_to_msecs(jiffies - cmd->jiffies_at_alloc);
 	char buf[80];
 
 	__scsi_format_command(buf, sizeof(buf), cmd->cmnd, cmd->cmd_len);
-	seq_printf(m, ", .cmd=%s", buf);
+	seq_printf(m, ", .cmd=%s, .retries=%d, allocated %d.%03d s ago", buf,
+		   cmd->retries, msecs / 1000, msecs % 1000);
 }