net/sntp.c: move ifdef into Makefile COBJS-$(...)

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>
diff --git a/net/Makefile b/net/Makefile
index 0eee330..d341874 100644
--- a/net/Makefile
+++ b/net/Makefile
@@ -33,7 +33,7 @@
 COBJS-y += rarp.o
 COBJS-y += eth.o
 COBJS-y += nfs.o
-COBJS-y += sntp.o
+COBJS-$(CONFIG_CMD_SNTP) += sntp.o
 
 COBJS	:= $(COBJS-y)
 SRCS	:= $(COBJS:.o=.c)