brcm: Add NVRAM for Vamrs 96boards Rock960

The 96boards Rock960 has a Cypress 4356 WiFi module, this adds the
a NVRAM based on the downstream NVRAM.

https://people.linaro.org/~manivannan.sadhasivam/rock960_wifi/brcmfmac4356-sdio.txt



Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: Sahaj Sarup <sahaj.sarup@linaro.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Josh Boyer <jwboyer@kernel.org>