ARM: shmobile: kzm9g-reference: add AS3711 and CPUFreq DT bindings

This adds DT bindings for an AS3711 PMIC, used for supplying power to the
CPU, some peripherals and the backlight, as well as extends the cpu0 DT
node with OPPs and a reference to the PMIC to support the CPUFreq and
CPU DVFS functions.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski+renesas@gmail.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>