sim: Added library include to fix build errors on clang-703.0.31

The use of array tuples, requires an explicit include of the array library

Change-Id: I06730051777a97edf80e41a5604184b387b12239
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>

sim: added missing include to mathexpr.hh

mathexpr.hh uses std::function<> but was not including the appropriate
header, which resulted in an error

build/ARM/sim/mathexpr.hh:51:18: error: 'function' in namespace 'std'
does not name a template type
typedef std::function<double(std::string)> EvalCallback;

This commit adds the missing include.

Change-Id: I6c01d77d4354c6de838538f137a38f75f9866166
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>

sim: Adding support for power models

This patch adds some basic support for power models in gem5.

The power interface is defined so it can interact with thermal
models as well. It implements a simple power evaluator that
can be used for simple power models that express power in the
form of a math expression. These expressions can use stats
within the same SimObject (or down its hierarchy) and some
magic variables such as "temp" for temperature.
In future patches we will extend this functionality to allow
slightly more complex expressions.

The model allows it to be extended to use other kinds of models.

Change-Id: I76752f9638b6815e229fd74cdcb7721a305cbc4b

power: Add support for power models

This patch adds some basic support for power models in gem5.

The power interface is defined so it can interact with thermal
models as well. It implements a simple power evaluator that
can be used for simple power models that express power in the
form of a math expression. These expressions can use stats
within the same SimObject (or down its hierarchy) and some
magic variables such as "temp" for temperature.
In future patches we will extend this functionality to allow
slightly more complex expressions.

The model allows it to be extended to use other kinds of models.

Finally, the thermal model is updated to use the power usage as input.