ARM: shmobile: r8a7791/koelsch dts: Add DVFS parameters into cpu0 node for r8a7791

Add needed information inside CPU0 for the generic cpufreq-cpu0 driver.

- voltage-tolerance = 1%
  It reflects the tolerance for the CPU voltage defined inside the OPP
  table. Due to the lack of proper OPP definition, use an arbitrary safe
  value.
- clock-latency = 300 us
  Approximate worst-case latency to do a full DVFS transition for every
  OPPs. Due to the lack of HW information, use an arbitrary safe value.
  Note: The term transition-latency will be more accurate to define this
  value since the clock transition latency is not the only parameter that
  will define the overall DVFS transition.
- operating-points = < kHz - uV >
  List of 6 operating points. All of them are using the same voltage
  since DVS is not supported in R-CAR Gen2.
- clocks
  phandle to the CPU clock source. This clock source is used for all the
  2 CortexA15 located inside the same cluster.

Signed-off-by: Gaku Inami <gaku.inami.xw@bp.renesas.com>
Acked-by: Magnus Damm <damm@opensource.se>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>