kbuild: Fix net/8022 selections

Patch by Keith Owens, with slight modifications.
His description:

The problem is net/802/Makefile which includes p8022 for any of
CONFIG_LLC, CONFIG_TR, CONFIG_IPX or CONFIG_ATALK.  p8022 calls
llc_register_sap which is in ext8022.o, that file is built by
net/core/Makefile but only for CONFIG_LLC.  It worked before because of
the wrong test in net/core/Makefile which always built ext8022.o.

net/802/Makefile

@@ -6,6 +6,7 @@ export-objs		:= llc_macinit.o p8022.o psnap.o
 
 obj-y			:= p8023.o
 
+# Check the p8022 selections against net/core/Makefile.
 obj-$(CONFIG_SYSCTL)	+= sysctl_net_802.o
 obj-$(CONFIG_LLC)	+= p8022.o psnap.o llc_sendpdu.o llc_utility.o \
 			   		   cl2llc.o llc_macinit.o	

net/core/Makefile

@@ -16,7 +16,8 @@ obj-$(CONFIG_FILTER) += filter.o
 
 obj-$(CONFIG_NET) += dev.o dev_mcast.o dst.o neighbour.o rtnetlink.o utils.o
 
-ifneq ($(CONFIG_LLC),n)
+# See p8022 in net/802/Makefile for config options to check
+ifneq ($(CONFIG_LLC)$(CONFIG_TR)$(CONFIG_IPX)$(CONFIG_ATALK),)
 obj-y += ext8022.o
 endif