brcm: add symlink for Pi Zero 2 W NVRAM file

The Raspberry Pi Zero 2 W comes with two possible WiFi modules.
One of them is the same module as shipped in the original
Raspberry Pi 3B and Zero W so lets link them so the devices
with that module will work out of the box.

Signed-off-by: Peter Robinson <pbrobinson@gmail.com>
Signed-off-by: Josh Boyer <jwboyer@kernel.org>