arm64: topology: Tell the scheduler about the relative power of cores

arm64: topology: Tell the scheduler about the relative power of cores

In heterogeneous systems like big.LITTLE systems the scheduler will be
able to make better use of the available cores if we provide power numbers
to it indicating their relative performance. Do this by parsing the CPU
nodes in the DT.

This code currently has no effect as no information on the relative
performance of the cores is provided.

Signed-off-by: Mark Brown <broonie@linaro.org>