trace: energy_model: Add trace event for EM runtime modifications

The Energy Model (EM) supports runtime modifications. Track the changes
in order to do post-processing analysis. Don't use arrays in the trace
event, since they are not properly supported by the tools. Instead use
simple "unroll" with emitting the trace event for each EM array entry
with proper ID information.

Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>