TL-SG2218(UN)_V1_20210514

New Feature/Enhancement:
1. Optimize the switch's performance.
2. Improve the compatibility of the firmware.
3. Fix the bug that the traffic statistics were not working.

Notes:
1. For TL-SG2218(UN) 1.0 only.
2. This firmware is fully adapted to Omada SDN Controller v4.3.5.
3.Please upgrade the switch to the middle firmware Build 20210407 first before upgrading to this firmware or later one.