ARM: dts: am437x-gp-evm: disable DDR regulator in rtc-only/poweroff mode

Without this, the memory will remain active during poweroff consuming
extra power.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
Signed-off-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/boot/dts/am437x-gp-evm.dts

@@ -540,6 +540,9 @@
 			regulator-state-mem {
 				regulator-on-in-suspend;
 			};
+			regulator-state-disk {
+				regulator-off-in-suspend;
+			};
 		};
 
 		dcdc5: regulator-dcdc5 {