tmpfiles: don't compare errno with negative value

Follow-up for 677430b

(cherry picked from commit d8f5a31)

src/tmpfiles/tmpfiles.c

@@ -2402,7 +2402,7 @@ static int item_do(
 
                         de_fd = openat(fd, de->d_name, O_NOFOLLOW|O_CLOEXEC|O_PATH);
                         if (de_fd < 0) {
-                                if (errno != -ENOENT)
+                                if (errno != ENOENT)
                                         q = log_error_errno(errno, "Failed to open file '%s': %m", de->d_name);
                         } else {
                                 _cleanup_free_ char *de_path = NULL;