cmd_net: drop spurious comma in U_BOOT_CMD

Building for boards that have CONFIG_CMD_CDP enabled fail with:
cmd_net.c:301: error: expected expression before ',' token

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

common/cmd_net.c

@@ -297,7 +297,7 @@ 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",
+	"Perform CDP network configuration"
 );
 #endif