wl1251: Set generated MAC address back to NVS data

In case there is no valid MAC address kernel generates random one. This
patch propagate this generated MAC address back to NVS data which will be
uploaded to wl1251 chip. So HW would have same MAC address as linux kernel
uses.

This should not change any functionality, but it is better to tell wl1251
correct mac address since beginning of chip usage.

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>