TF-A works on a 6 month release cadence and we typically update the gcc toolchain to the latest released version along with the TF-A release. gcc versions we use are downloaded from https://developer.arm.com/tools-and-software/open-source-software/developer-tools/gnu-toolchain/downloads.
Currently we don't update the toolchain to any versions newer than the one released here. We used the version 10.3-2021.07 with TF-A v2.6 release and will be updating to version 11.2-2022.02 with our upcoming v2.7 release which is planned for the end of May, 2022.