firewire: net: fix use after free

commit 8987583366ae9e03c306c2b7d73bdb952df1d08d upstream.

Commit 8408dc1c14c1 "firewire: net: use dev_printk API" introduced a
use-after-free in a failure path.  fwnet_transmit_packet_failed(ptask)
may free ptask, then the dev_err() call dereferenced it.  The fix is
straightforward; simply reorder the two calls.

Change-Id: I84c243f034fb487520500f9b8fb0591799a249db
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>