net: reduce USB network driver config options.

USB network drivers are already handled in drivers/net/usb/Kconfig.
Let's save the maintenance burden of dependencies in drivers/net/Makefile.

The newly introduced USB_NET_DRIVERS umbrella config option defaults
to 'y' so as to minimize the changes of behavior.
Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/Makefile

@@ -61,14 +61,7 @@ obj-$(CONFIG_VMXNET3) += vmxnet3/
 obj-$(CONFIG_XEN_NETDEV_FRONTEND) += xen-netfront.o
 obj-$(CONFIG_XEN_NETDEV_BACKEND) += xen-netback/
 
-obj-$(CONFIG_USB_CATC)          += usb/
-obj-$(CONFIG_USB_KAWETH)        += usb/
-obj-$(CONFIG_USB_PEGASUS)       += usb/
-obj-$(CONFIG_USB_RTL8150)       += usb/
-obj-$(CONFIG_USB_HSO)		+= usb/
-obj-$(CONFIG_USB_USBNET)        += usb/
-obj-$(CONFIG_USB_IPHETH)        += usb/
-obj-$(CONFIG_USB_CDC_PHONET)   += usb/
+obj-$(CONFIG_USB_NET_DRIVERS) += usb/
 
 obj-$(CONFIG_HYPERV_NET) += hyperv/
 obj-$(CONFIG_NTB_NETDEV) += ntb_netdev.o

drivers/net/usb/Kconfig

 #
 # USB Network devices configuration
 #
-comment "Networking support is needed for USB Network Adapter support"
-	depends on USB && !NET
+comment "Host-side USB support is needed for USB Network Adapter support"
+	depends on !USB && NET
 
-menu "USB Network Adapters"
+menuconfig USB_NET_DRIVERS
+	bool "USB Network Adapters"
+	default y
 	depends on USB && NET
 
+if USB_NET_DRIVERS
+
 config USB_CATC
 	tristate "USB CATC NetMate-based Ethernet device support"
 	select CRC32
@@ -568,5 +572,4 @@ config USB_VL600
 
 	  http://ubuntuforums.org/showpost.php?p=10589647&postcount=17
 
-
-endmenu
+endif # USB_NET_DRIVERS