usb: gadget: Convert USB_ETHER to Kconfig

The USB Ethernet gadget option has not yet been moved to Kconfig, let's
deal with that.

Reviewed-by: Ɓukasz Majewski <lukma@denx.de>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
diff --git a/drivers/usb/gadget/Kconfig b/drivers/usb/gadget/Kconfig
index 510efd6..6558d24 100644
--- a/drivers/usb/gadget/Kconfig
+++ b/drivers/usb/gadget/Kconfig
@@ -121,6 +121,18 @@
 
 endif # USB_GADGET_DOWNLOAD
 
+config USB_ETHER
+	bool "USB Ethernet Gadget"
+	help
+	  Creates an Ethernet network device through a USB peripheral
+	  controller. This will create a network interface on both the device
+	  (U-Boot) and the host (remote device) that can be used just like any
+	  other nework interface.
+	  It will bind on the peripheral USB controller, ignoring the USB hosts
+	  controllers in the system.
+
+if USB_ETHER
+
 config USBNET_DEVADDR
 	string "USB Gadget Ethernet device mac address"
 	default "de:ad:be:ef:00:01"
@@ -135,4 +147,6 @@
 	  Ethernet MAC address of the host-side (ie. remote device's) MAC
 	  address of the usb_ether interface
 
+endif # USB_ETHER
+
 endif # USB_GADGET