ssb: drop BCM4328 hack for SPROM revision

This hacks leads to incorrect SPROM parsing for me and reading for example MAC
as: 00:00:00:54:00:00. Michael G. who introduced this confirmed it is not
needed anymore.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Tested-by: Michael Gerdau <mgd@qata.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>