tmpfiles: simplify mountpoint detection

No functional change. Just a simplification. A || (!A && B) is
the same as A || B

Introduced in 78a92a5a2306709e4587e332728a76901323ade9
diff --git a/src/tmpfiles/tmpfiles.c b/src/tmpfiles/tmpfiles.c
index f636a4d..09b6ca5 100644
--- a/src/tmpfiles/tmpfiles.c
+++ b/src/tmpfiles/tmpfiles.c
@@ -1585,8 +1585,7 @@
         if (fstatat(dirfd(d), "..", &ps, AT_SYMLINK_NOFOLLOW) != 0)
                 return log_error_errno(errno, "stat(%s/..) failed: %m", i->path);
 
-        mountpoint = s.st_dev != ps.st_dev ||
-                     (s.st_dev == ps.st_dev && s.st_ino == ps.st_ino);
+        mountpoint = s.st_dev != ps.st_dev || s.st_ino == ps.st_ino;
 
         log_debug("Cleanup threshold for %s \"%s\" is %s",
                   mountpoint ? "mount point" : "directory",