ARM: dts: exynos: Add DMC bus frequency for exynos3250-rinato/monk

This patch adds the DMC (Dynamic Memory Controller) bus frequency node
which includes the devfreq-events and regulator properties. The bus
frequency support the DVFS (Dynamic Voltage Frequency Scaling) feature
with ondemand governor.

The devfreq-events (ppmu_dmc0*) can monitor the utilization of DMC bus
on runtime and the buck1_reg (VDD_MIF power line) supplies the power to
the DMC block.

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Reviewed-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Acked-by: MyungJoo Ham <myungjoo.ham@samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>