Remove direct logging

Drop perror() calls from GSMTAP code: it's application job to do the
proper logging - library code should not write to stdout/stderr
directly.

Change-Id: Ifa149e65d76c6e64fda2946725c16672233aff2e
diff --git a/src/gsmtap_util.c b/src/gsmtap_util.c
index 66abdf1..ab4a28e 100644
--- a/src/gsmtap_util.c
+++ b/src/gsmtap_util.c
@@ -286,11 +286,9 @@
 
 	rc = write(ofd->fd, msg->data, msg->len);
 	if (rc < 0) {
-		perror("writing msgb to gsmtap fd");
 		return rc;
 	}
 	if (rc != msg->len) {
-		perror("short write to gsmtap fd");
 		return -EIO;
 	}
 
@@ -308,7 +306,6 @@
 
 	rc = read(fd->fd, buf, sizeof(buf));
 	if (rc < 0) {
-		perror("reading from gsmtap sink fd");
 		return rc;
 	}
 	/* simply discard any data arriving on the socket */