tc0: update documentation for 2021.02.09 platform release

Updated change-log, release_notes, user-guide for tc0 with new
software/hardware features added and its changes from the previous release.

Signed-off-by: Arunachalam Ganapathy <arunachalam.ganapathy@arm.com>
Change-Id: I7cbbc19cf9fff3c82e19b91f9b5306c056ad9640