cmd_net.c: fix build breakage

Commit 722b061b "autocomplete: remove runtime handler install" caused
some boards (like NETTA2_V2) to break with errors like these:

cmd_net.c:296: error: expected expression before ',' token

Fix this.
Signed-off-by: NWolfgang Denk <wd@denx.de>
Cc: Mike Frysinger <vapier@gentoo.org>

common/cmd_net.c

@@ -296,6 +296,7 @@ int do_cdp (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 U_BOOT_CMD(
 	cdp,	1,	1,	do_cdp,
 	"Perform CDP network configuration",
+	"\n"
 );
 #endif