bsc: Do not use strdup on argv parameter

Fixes: Coverity CID 1206578

openbsc/src/osmo-bsc/osmo_bsc_main.c

@@ -116,7 +116,7 @@ static void handle_options(int argc, char **argv)
 			daemonize = 1;
 			break;
 		case 'c':
-			config_file = strdup(optarg);
+			config_file = optarg;
 			break;
 		case 'T':
 			log_set_print_timestamp(osmo_stderr_target, 1);