ARM: dts: at91: sama5d2_xplained: Add proper regulator states for suspend-to-mem

When entering suspend-to-mem, all PMIC outputs are disabled except
VDDIODDR which is put in power saving mode, and whose voltage is
increased (probably to counter the poor accuracy of power saving mode).

Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
[claudiu.beznea@microchip.com: use regulator-changeable-in-suspend,
 regulator-suspend-max-microvolt, regulator-suspend-max-microvolt,
 use macros for regulators' states, add regulator-inital-state]
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Ludovic Desroches <ludovic.desroches@microchip.com>