drivers/net/Makefile: conditionally descend to wireless

Don't descend to wireless unless it is actually used.
Signed-off-by: Nicolas Kaiser <nikai@nikai.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/Makefile

@@ -276,7 +276,7 @@ obj-$(CONFIG_USB_USBNET)        += usb/
 obj-$(CONFIG_USB_ZD1201)        += usb/
 obj-$(CONFIG_USB_IPHETH)        += usb/
 
-obj-y += wireless/
+obj-$(CONFIG_WLAN) += wireless/
 obj-$(CONFIG_NET_TULIP) += tulip/
 obj-$(CONFIG_HAMRADIO) += hamradio/
 obj-$(CONFIG_IRDA) += irda/