net: l3mdev: use obj-$(CONFIG_NET_L3_MASTER_DEV) form in net/Makefile

CONFIG_NET_L3_MASTER_DEV is a bool option. Change the ifeq conditional
to the standard obj-$(CONFIG_NET_L3_MASTER_DEV) form.

Use obj-y in net/l3mdev/Makefile because Kbuild visits this Makefile
only when CONFIG_NET_L3_MASTER_DEV=y.
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>
Reviewed-by: NDavid Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/20210125231659.106201-4-masahiroy@kernel.orgSigned-off-by: NJakub Kicinski <kuba@kernel.org>

net/Makefile

@@ -73,9 +73,7 @@ obj-$(CONFIG_MPLS)		+= mpls/
 obj-$(CONFIG_NET_NSH)		+= nsh/
 obj-$(CONFIG_HSR)		+= hsr/
 obj-$(CONFIG_NET_SWITCHDEV)	+= switchdev/
-ifneq ($(CONFIG_NET_L3_MASTER_DEV),)
-obj-y				+= l3mdev/
-endif
+obj-$(CONFIG_NET_L3_MASTER_DEV)	+= l3mdev/
 obj-$(CONFIG_QRTR)		+= qrtr/
 obj-$(CONFIG_NET_NCSI)		+= ncsi/
 obj-$(CONFIG_XDP_SOCKETS)	+= xdp/

net/l3mdev/Makefile

@@ -3,4 +3,4 @@
 # Makefile for the L3 device API
 #
 
-obj-$(CONFIG_NET_L3_MASTER_DEV) += l3mdev.o
+obj-y += l3mdev.o