ieee1394: save one word in struct hpsb_host

hpsb_host.config_roms is a bitfield of which only one bit is currently
used.  hpsb_host.update_config_rom is only a Boolean.  Neither one is
accessed in hot code paths or with alignment requirements.

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