Why I did it
This SAI change is to Enable TD2 platforms to also be able to handle VFP-based sub-interfaces.
This is the feature that is also needed for TD2 platforms.
How to verify it
Guohan and Team has validated this feature change on TD2 platforms
This is to pick up BRCM SAI 4.3.3.5-2 which contains 2 main changes:
1. hsdk-6.5.21-p1.patch (to address some field problems related to SDK issue.
2. Fix for CS00012097141 (remove some unnecessary debug setting that was causing non functional impacting problem at boot time)
Preliminary tests looks fine. BGP neighbors were all up with proper routes programmed
interfaces are all up
Manually ran the following test cases on S6100 DUT and all passed:
```
ipfwd/test_dir_bcast.py
fib/test_fib.py
vxlan/test_vxlan_decap.py
decap/test_decap.py
fdb/test_fdb.py
```
202012 branch is using reproducible build. The versions-py3 file must contains correct pip3 package version. Otherwise we will get a build error
```
Step 31/74 : RUN pip3 install scapy==2.4.4 pyroute2==0.5.14 netifaces==0.10.9
---> Running in d7a2401dd21d
Collecting scapy==2.4.4
Downloading scapy-2.4.4.tar.gz (1.0 MB)
Collecting pyroute2==0.5.14
Downloading pyroute2-0.5.14.tar.gz (873 kB)
ERROR: Cannot install netifaces==0.10.9 because these package versions have conflicting dependencies.
The conflict is caused by:
The user requested netifaces==0.10.9
The user requested (constraint) netifaces==0.10.7
To fix this you could try to:
1. loosen the range of package versions you've specified
2. remove package versions to allow pip attempt to solve the dependency conflict
ERROR: ResolutionImpossible: for help visit https://pip.pypa.io/en/latest/user_guide/#fixing-conflicting-dependencies
The command '/bin/sh -c pip3 install scapy==2.4.4 pyroute2==0.5.14 netifaces==0.10.9' returned a non-zero code: 1
[ FAIL LOG END ] [ target/docker-sonic-vs.gz ]
```
