ARM: dts: exynos: Add regulator suspend configuration to Arndale Octa board

Add the PMIC regulator suspend configuration to Arndale Octa board to
reduce power usage during suspend and keep necessary regulators on.  The
configuration is based on vendor (Insignal) reference kernel and the
board datasheet.  Comparing to vendor kernel, additionally turn off in
suspend all regulators controlled by external pin (LDO3, LDO7, LDO18 and
buck10).

This is purely for hardware description because board does not support
Suspend to RAM and the S2MPS11 driver does not support
"regulator-on-in-suspend" property.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>