Update Foundation, AEM and Cortex Models versions

Trusted Firmware has been tested as part of its CI system against Cortex
and Foundation models in the 11.0 Model release available on
developer.arm.com. Trusted Firmware has also been tested against the v8.5
AEM model.

This patch updates the user guide documentation to reflect the version of
the Foundation, AEM and Cortex Models that Trusted Firmware has been
tested against.

Change-Id: I3b5b4d1e4220bda1dcc88aa9cfa01fa711ed92cd
Signed-off-by: David Cunado <david.cunado@arm.com>