ieee1394: hl_irqs_lock is taken in hardware interrupt context

ohci1394 and pcilynx call highlevel_host_reset from their hardware
interrupt handler (via hpsb_selfid_complete).  Therefore all readers and
writers of hl_irqs_lock have to disable interrupts.  Reported by Jiri
Slaby and J. A. Magallon.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
Signed-off-by: Ben Collins <bcollins@ubuntu.com>