ssb: Add new SPROM structure while keeping the old

The SPROM's for various devices utilizing the Sonics Silicon Backplane come
with various revisions. The Revision 2 SPROM inherited the data layout of 1, and
Revision 3 inherited the layout of 2. The first instance of Revision 4 has
now been found in a BCM4328 wireless LAN card. This device does not inherit any
layout from previous versions. Although it was possible to create a data
structure that kept all the old layouts, we decided to start fresh, keep only
those SPROM variables that are used by the drivers that utilize ssb, and to
do the conversion in such a manner that neither compilation or execution will
be affected if a bisection lands in the middle of these changes, while keeping
the patches as small as possible.

In this patch, the sprom structures are changed while maintaining the old ones.

Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>