dt-bindings: nvmem: add Broadcom's NVRAM

Broadcom's NVRAM structure contains device data and can be accessed
using I/O mapping.

Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20210330111241.19401-5-srinivas.kandagatla@linaro.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>