linux: fix kmod-usb-net-* for >= 3.17

Kernel commit 1bb5a356c3ea ("net: reduce USB network driver config
options.") hid the USB network drivers behind the new config symbol
CONFIG_USB_NET_DRIVERS.

Signed-off-by: Bjørn Mork <bjorn@mork.no>

SVN-Revision: 44460

package/kernel/linux/modules/usb.mk

@@ -992,7 +992,8 @@ $(eval $(call KernelPackage,usb-atm-cxacru))
 define KernelPackage/usb-net
   TITLE:=Kernel modules for USB-to-Ethernet convertors
   DEPENDS:=+kmod-mii
-  KCONFIG:=CONFIG_USB_USBNET
+  KCONFIG:=CONFIG_USB_USBNET \
+	CONFIG_USB_NET_DRIVERS@ge3.18
   AUTOLOAD:=$(call AutoProbe,usbnet)
   FILES:=$(LINUX_DIR)/drivers/$(USBNET_DIR)/usbnet.ko
   $(call AddDepends/usb)