ieee1394: sbp2: consolidate log levels

Replace some calls to SBP2_ERR and SBP2_WARN by SBP2_INFO.
Remove logging macros SBP2_NOTICE and SBP2_WARN.
Remove direct usage of HPSB_ logging macros.

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