docs(threat-model): broaden the scope of threat #05

 - Cite crash reports as an example of sensitive
   information. Previously, it might have sounded like this was the
   focus of the threat.

 - Warn about logging high-precision timing information, as well as
   conditionally logging (potentially nonsensitive) information
   depending on sensitive information.

Change-Id: I33232dcb1e4b5c81efd4cd621b24ab5ac7b58685
Signed-off-by: Sandrine Bailleux <sandrine.bailleux@arm.com>