net/Makefile: conditionally descend to wireless and ieee802154

Don't descend to wireless and ieee802154 unless they are actually used.
Signed-off-by: Nicolas Kaiser <nikai@nikai.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/Makefile

@@ -50,7 +50,7 @@ endif
 obj-$(CONFIG_IP_DCCP)		+= dccp/
 obj-$(CONFIG_IP_SCTP)		+= sctp/
 obj-$(CONFIG_RDS)		+= rds/
-obj-y				+= wireless/
+obj-$(CONFIG_WIRELESS)		+= wireless/
 obj-$(CONFIG_MAC80211)		+= mac80211/
 obj-$(CONFIG_TIPC)		+= tipc/
 obj-$(CONFIG_NETLABEL)		+= netlabel/
@@ -61,7 +61,7 @@ obj-$(CONFIG_CAIF)		+= caif/
 ifneq ($(CONFIG_DCB),)
 obj-y				+= dcb/
 endif
-obj-y				+= ieee802154/
+obj-$(CONFIG_IEEE802154)	+= ieee802154/
 
 ifeq ($(CONFIG_NET),y)
 obj-$(CONFIG_SYSCTL)		+= sysctl_net.o