net: Move CDP out of net.c

Separate this functionality out of the net.c behemoth

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/net/Makefile b/net/Makefile
index 5901046..b350bfc 100644
--- a/net/Makefile
+++ b/net/Makefile
@@ -28,6 +28,7 @@
 LIB	= $(obj)libnet.o
 
 COBJS-$(CONFIG_CMD_NET)  += bootp.o
+COBJS-$(CONFIG_CMD_CDP)  += cdp.o
 COBJS-$(CONFIG_CMD_DNS)  += dns.o
 COBJS-$(CONFIG_CMD_NET)  += eth.o
 COBJS-$(CONFIG_CMD_NET)  += net.o