Patch for enabling USB3 on M2 on TX2 4GB model running latest JetPack 4.5.1?

Hi,
There is no existing patch. You would need to check adaptation guide and modify defice tree accordingly. There are reference posts of modifying device tree on r32 releases:
USB not working in Jetson TX2 - R32.2 - #2 by DaneLLL
Jetson TX2 USB 2/3 connection - #2 by DaneLLL