arm64: dts: renesas: salvator-common: Add PMIC DDR Backup Power config

On Salvator-X(S), all of the DDR0, DDR1, DDR0C, and DDR1C power rails
need to be kept powered when backup mode is enabled.  Reflect this in
the "rohm,ddr-backup-power" property for the BD9571MWV PMIC node.

The accessory power switch (SW23) is a toggle switch, hence specify
"rohm,rstbmode-level".
Signed-off-by: NGeert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: NSimon Horman <horms+renesas@verge.net.au>

arch/arm64/boot/dts/renesas/salvator-common.dtsi

@@ -374,6 +374,8 @@
 		#interrupt-cells = <2>;
 		gpio-controller;
 		#gpio-cells = <2>;
+		rohm,ddr-backup-power = <0xf>;
+		rohm,rstbmode-level;
 
 		regulators {
 			dvfs: dvfs {