[][openwrt][mt7988][tops][split release and develop package]

[Description]
Change Makefile structure to support release and developing package.

The first version of this package only support release driver but can
support release and developing firmware.
However, this would lead to some unsynchronized driver and firmware issue
that eventually cause tunnel offload feature failed.

To solve this problem, we provide another driver package that is support
developing driver and firmware.

The new architecture only let customer be able to select release driver and
firmware. For internal development, we can select latest driver and
firmware.

[Release-log]
N/A

Change-Id: I938f183784c65e022945bb1258a05887b819760e
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/7950733
3 files changed