Fix logging in xf86-input-mfndev

Use X's logging function instead of plain perror, to ensure the message
is written in appropriate Xorg's log.

xf86-input-mfndev/src/qubes.c

@@ -390,7 +390,7 @@ int connect_unix_socket(QubesDevicePtr pQubes)
     struct sockaddr_un remote;
 
     if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {
-        perror("socket");
+        xf86Msg(X_ERROR, "socket(%s): %s\n", pQubes->device, strerror(errno));
         return -1;
     }
 
@@ -399,7 +399,7 @@ int connect_unix_socket(QubesDevicePtr pQubes)
     strncpy(remote.sun_path, pQubes->device, sizeof(remote.sun_path));
     len = strlen(remote.sun_path) + sizeof(remote.sun_family);
     if (connect(s, (struct sockaddr *) &remote, len) == -1) {
-        perror("connect");
+        xf86Msg(X_ERROR, "connect(%s): %s\n", pQubes->device, strerror(errno));
         close(s);
         return -1;
     }