MIPS: ath79: add common USB Host Controller device

Add common platform_device and helper code to make the registration of
the built-in USB controllers easier on the board which are using them.
Also register the USB controller on the AP81 and PB44 boards.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Signed-off-by: Imre Kaloz <kaloz@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2442/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
diff --git a/arch/mips/ath79/Makefile b/arch/mips/ath79/Makefile
index c33d465..57188b6 100644
--- a/arch/mips/ath79/Makefile
+++ b/arch/mips/ath79/Makefile
@@ -20,6 +20,7 @@
 obj-$(CONFIG_ATH79_DEV_GPIO_BUTTONS)	+= dev-gpio-buttons.o
 obj-$(CONFIG_ATH79_DEV_LEDS_GPIO)	+= dev-leds-gpio.o
 obj-$(CONFIG_ATH79_DEV_SPI)		+= dev-spi.o
+obj-$(CONFIG_ATH79_DEV_USB)		+= dev-usb.o
 
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