ieee1394: regression in 2.6.25: updates should happen before probes

Regression since commit 73cf6023,
"ieee1394: use class iteration api":  The two loops for (1.) driver
updates and (2.) driver probes were replaced by a single loop with
bogus needs_probe checks.  Hence updates and probes were now intermixed,
and especially sbp2 updates (reconnects) held up longer than necessary.

While we fix it, change the needs_probe flag to bool type for clarity.

Tested by Damien Benoist.

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