This patch adds PPMU (Platform Performance Monitoring Unit) Device-tree node
to measure the utilization of each IP in Exynos SoC.

- PPMU_D{0|1}_CPU are used to measure the utilization of MIF (Memory Interface)
  block with VDD_MIF power source.
- PPMU_D{0|1}_GENERAL are used to measure the utilization of INT(Internal)
  block with VDD_INT power source.
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>