MIPS: ath79: Register the wireless MAC device on the AP121 board

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Cc: Imre Kaloz <kaloz@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/3032/


Signed-off-by: Ralf Baechle <ralf@linux-mips.org>