ieee1394: mark bus_info_data as a __be32 array

Two access functions get_max_rom and set_hw_config_rom are
changed to take __be32 as well.  Only bus_info_data was
ever passed in so this is OK.  All other uses of bus_info_data
treated it as a be32 value already.

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>