ext, mem: Pull DRAMPower SHA 90d6290 and rebase

This patch syncs the DRAMPower library of gem5 to the
external github (https://github.com/ravenrd/DRAMPower).

The version pulled in is the commit:
90d6290f802c29b3de9e10233ceee22290907ce6
from 30th Oct. 2016.

This change also modifies the DRAM Ctrl interaction with the
DRAMPower, due to changes in the lib API in the above version.

Previously multiple functions were called to prepare the power
lib before calling the function that would calculate the enery. With
the new API, these functions are encompassed inside the function to
calculate the energy and therefore should now be removed from the
DRAM controller.

The other key difference is the introduction of a new function called
calcWindowEnergy which can be useful for any system that wants
to do measurements over intervals. For gem5 DRAM ctrl that means we
now need to accumulate the window energy measurements into the total
stat.

Change-Id: I3570fff2805962e166ff2a1a3217ebf2d5a197fb
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/5724
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>

ext: Update DRAMPower

Sync DRAMPower to external tool

This patch syncs the DRAMPower library of gem5 to the external
one on github (https://github.com/ravenrd/DRAMPower) of which
I am a maintainer.

The version used is the commit:
902a00a1797c48a9df97ec88868f20e847680ae6
from 07. May. 2016.

Committed by Jason Lowe-Power <jason@lowepower.com>

ext: Add DRAMPower to enable on-line DRAM power modelling

This patch adds the open-source (BSD 3-clause) tool DRAMPower, commit
8d3cf4bbb10aa202d850ef5e5e3e4f53aa668fa6, to be built as a part of the
simulator. We have chosen this specific version of DRAMPower as it
provides the necessary functionality, and future updates will be
coordinated with the DRAMPower development team. The files added only
include the bits needed to build the library, thus excluding all
memory specifications, traces, and the stand-alone DRAMPower
command-line tool.

A future patch includes the DRAMPower functionality in the DRAM
controller, to enable on-line DRAM power modelling, and avoid using
post-processing of traces.