swconfig: improve usability when switch device incorrect

http://patchwork.openwrt.org/patch/4701/

Signed-off-by: Andreas Mohr <andim2@users.sf.net>

SVN-Revision: 39229

package/network/config/swconfig/src/cli.c

@@ -270,7 +270,7 @@ int main(int argc, char **argv)
 
 	dev = swlib_connect(cdev);
 	if (!dev) {
-		fprintf(stderr, "Failed to connect to the switch\n");
+		fprintf(stderr, "Failed to connect to the switch. Use the \"list\" command to see which switches are available.\n");
 		return 1;
 	}