infra/rdn2: updates for RD-INFRA-2021.08.11 release

For the RD-INFRA-2021.08.11 release, include the documentation about
using non-discoverable devices connected to IO virtualization block.
In addition to this, update the expected FVP version to be used
along with software tagged as RD-INFRA-2021.08.11.

Signed-off-by: Thomas Abraham <thomas.abraham@arm.com>
Change-Id: Ic6afb1a6f99c403db00a5f46e27ab52a2c54037c