This patch adds the generic exynos bus frequency driver for AMBA AXI bus
of sub-blocks in exynos SoC with DEVFREQ framework. The Samsung Exynos SoC
have the common architecture for bus between DRAM and sub-blocks in SoC.
This driver can support the generic bus frequency driver for Exynos SoCs.

In devicetree, Each bus block has a bus clock, regulator, operation-point
and devfreq-event devices which measure the utilization of each bus block.

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
[m.reichl and linux.amoon: Tested it on exynos4412-odroidu3 board]
Tested-by: Markus Reichl <redacted>
Tested-by: Anand Moon <redacted>
---
 drivers/devfreq/Kconfig      |  15 ++
 drivers/devfreq/Makefile     |   1 +
 drivers/devfreq/exynos-bus.c | 443 +++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 459 insertions(+)
 create mode 100644 drivers/devfreq/exynos-bus.c

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>