MIPS: BCM47xx: Fill values for b43 into SSB sprom

Fill the sprom with all available values from the nvram. Most of these
new values are needed for the b43 or b43legacy driver.

Parts of this patch have been in OpenWRT for a long time and were written
by Michael Buesch.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
To: linux-mips@linux-mips.org
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Patchwork: https://patchwork.linux-mips.org/patch/1846/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>