SSB: Change fallback sprom to callback mechanism.

SSB: Change fallback sprom to callback mechanism.

Some embedded devices like the Netgear WNDR3300 have two SSB based cards
without an own sprom on the pci bus. We have to provide two different
fallback sproms for these and this was not possible with the old solution.
In the bcm47xx architecture the sprom data is stored in the nvram in the
main flash storage. The architecture code will be able to fill the sprom
with the stored data based on the bus where the device was found.

The bcm63xx code should do the same thing as before, just using the new
API.

Acked-by: Michael Buesch <mb@bu3sch.de>
Cc: netdev@vger.kernel.org
Cc: linux-wireless@vger.kernel.org
Cc: Florian Fainelli <florian@openwrt.org>
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2362/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>