ARM: dts: stm32mp1: Add PSCI node access before relocation

Add node in DT and avoid error to search UCLASS_SYSRESET in
board_f.c::print_resetinfo() and lost 1.6s in U-Boot
for the trusted boot chain.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>

arch/arm/dts/stm32mp157-u-boot.dtsi

@@ -25,6 +25,11 @@
 		u-boot,dm-pre-reloc;
 	};
 
+	/* need PSCI for sysreset during board_f */
+	psci {
+		u-boot,dm-pre-proper;
+	};
+
 	reboot {
 		u-boot,dm-pre-reloc;
 	};