mips: bcm47xx: allow retrieval of complete nvram contents

Host platforms such as routers supported by OpenWrt can
support NVRAM reading directly from internal NVRAM store.
The brcmfmac for one requires the complete nvram contents
to select what needs to be sent to wireless device.

Signed-off-by: Arend van Spriel <arend@broadcom.com>
Signed-off-by: Hante Meuleman <meuleman@broadcom.com>
Reviewed-by: Arend Van Spriel <arend@broadcom.com>
Reviewed-by: Franky (Zhenhui) Lin <frankyl@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Reviewed-by: Daniel (Deognyoun) Kim <dekim@broadcom.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10093/


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