rts comand queuing we send the INQUIRY command "untagged" for
  LUN1 while we can send a tagged command to LUN0 at the same time.
  devinfo->cmnd is used for stashing the one "untagged" command.
- tag number is altered. If stream support is used then the tag number
  must match the stream number. Therefore we can't use tag 0 and must
  start at tag 1.
  In case we have untagged commands (at least the first command) we must
  be able to distinguish between command tag 0 (which becomes 1) and
  untagged command (which becomes curently also 1).
  The following tag numbers are used:
  0: never
  1: for untagged commands (devinfo->cmnd)
  2+: tagged commands.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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