sim: Added model type to power model

sim: Added model type to power model

Static, dynamic or all to differentiate between types of power models
so for example static models will not be asked for a dynamic power

Change-Id: I3a0385821f7c671aedddaebeb038c677367faa81
Reviewed-by: Sascha Bischoff <sascha.bischoff@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/8601
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>