firewire: fw-sbp2: fix another small generation access bug

queuecommand() looked at the remote and local node IDs before it read
the bus generation.  The corresponding race with sbp2_reconnect updating
these data was probably impossible to happen though because the current
code blocks the SCSI layer during reconnection.  However, better safe
than sorry, especially if someone later improves the code to not block
the SCSI layer.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>