MIPS: ath79: add common WMAC device for AR913X based boards

Add common platform_device and helper code to make the registration
of the built-in wireless MAC easier on the Atheros AR9130/AR9132
based boards. Also register the WMAC device on the AR81 board.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Cc: linux-mips@linux-mips.org
Cc: Imre Kaloz <kaloz@openwrt.org>,
Cc: Luis R. Rodriguez <lrodriguez@atheros.com>
Cc: Cliff Holden <Cliff.Holden@Atheros.com>
Cc: Kathy Giori <Kathy.Giori@Atheros.com>
Patchwork: https://patchwork.linux-mips.org/patch/1962/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/ath79/Makefile b/arch/mips/ath79/Makefile
index a245e36..c33d465 100644
--- a/arch/mips/ath79/Makefile
+++ b/arch/mips/ath79/Makefile
@@ -16,6 +16,7 @@
 # Devices
 #
 obj-y					+= dev-common.o
+obj-$(CONFIG_ATH79_DEV_AR913X_WMAC)	+= dev-ar913x-wmac.o
 obj-$(CONFIG_ATH79_DEV_GPIO_BUTTONS)	+= dev-gpio-buttons.o
 obj-$(CONFIG_ATH79_DEV_LEDS_GPIO)	+= dev-leds-gpio.o
 obj-$(CONFIG_ATH79_DEV_SPI)		+= dev-spi.o