firewire: Don't time out command orbs, leave that to the scsi stack.

The mod_timer based timing out of orb was a little to agressive and
would time out legit, but long-lived scsi cmds.  Besides, the scsi
stack keeps track of this already.  Since we're only timing out
management orbs, go back to wait_for_completion_timeout.

Signed-off-by: Kristian Høgsberg <krh@redhat.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>