firewire: core: wait for inaccessible devices after bus reset

When reread_config_rom() encountered a config rom that was marked as not
yet accessible, that device would be treated as "gone".  This would mean
that that device would effectively vanish until the next bus reset.

The correct way to handle this situation is the same as in
read_config_rom(), to treat this like other errors and to retry the read
later, when the (possibly changed) config rom is available.  The device
is marked "gone" only if it continues to return zero values after these
retries.

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