MIPS: BCM63XX: generate WLAN MAC address after registering ethernet devices.

In case the MAC address pool is not big enough to also register a WLAN device
prefer registering the Ethernet devices.

[ralf@linux-mips.org: Fixed formatting as per Sergei's complaint.]

Signed-off-by: Florian Fainelli <florian@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3013/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>