MIPS: BCM47XX: Make bcma init NVRAM instead of bcm47xx polling it

This drops ssb/bcma dependency and will allow us to make it a standalone
driver.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Cc: linux-mips@linux-mips.org
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Patchwork: https://patchwork.linux-mips.org/patch/8233/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>