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 <bart.vanassche@wdc.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>