*: use fopen_or_warn in few more places

diff --git a/networking/interface.c b/networking/interface.c
index 367d2b0..44bd8d3 100644
--- a/networking/interface.c
+++ b/networking/interface.c
@@ -560,9 +560,8 @@
 	if (!target)
 		proc_read = 1;
 
-	fh = fopen(_PATH_PROCNET_DEV, "r");
+	fh = fopen_or_warn(_PATH_PROCNET_DEV, "r");
 	if (!fh) {
-		bb_perror_msg("warning: cannot open %s, limiting output", _PATH_PROCNET_DEV);
 		return if_readconf();
 	}
 	fgets(buf, sizeof buf, fh);	/* eat line */