MIPS: BCM47xx: Move NVRAM driver to the drivers/firmware/

MIPS: BCM47xx: Move NVRAM driver to the drivers/firmware/

After Broadcom switched from MIPS to ARM for their home routers we need
to have NVRAM driver in some common place (not arch/mips/). As explained
in Kconfig, this driver is responsible for parsing SoC configuration
data that is passed to the kernel in flash from the bootloader firmware
called "CFE".

We were thinking about putting it in bus directory, however there are
two possible buses for MIPS: drivers/ssb/ and drivers/bcma/. So this
won't fit there and this is why I would like to move this driver to the
drivers/firmware/.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Reviewed-by: Paul Walmsley <paul@pwsan.com>
Cc: linux-mips@linux-mips.org
Cc: Hauke Mehrtens <hauke@hauke-m.de>
Cc: Seiji Aguchi <seiji.aguchi@hds.com>
Cc: Greg Kroah-Hartman <gregkh@suse.de>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Mike Waychison <mikew@google.com>
Cc: Roy Franz <roy.franz@linaro.org>
Cc: Matt Fleming <matt.fleming@intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Patchwork: https://patchwork.linux-mips.org/patch/10544/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>