Why I did it
XGS saibcm-modules 8.4 is needed. #14471
Work item tracking
Microsoft ADO (number only): 24917414
How I did it
Copy files from xgs SDK 8.4 repo and modify makefiles to build the image.
Upgrade version to 8.4.0.2 in saibcm-modules.mk.
How to verify it
Build a private image and run full qualification with it: https://elastictest.org/scheduler/testplan/650419cb71f60aa92c456a2b
2c0f4e57d7