generic: overlay: disable OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW

generic: overlay: disable OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW

The Kconfig symbol help text prompts:
  Disable this to get a possibly more secure configuration, but that
  might not be backward compatible with previous kernels.
  If backward compatibility is not an issue, then it is safe and
  recommended to say N here.

For OpenWrt, when updating firmware, we always update the kernel and
recreate the overlay partition. Therefore, compatibility is not a
problem.

Signed-off-by: Shiji Yang <yangshiji66@outlook.com>
Link: https://github.com/openwrt/openwrt/pull/23126
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>