dts: arm: stm32H5 reg definition for the st,stm32-xspi compatible

The st,stm32-xspi compatible is defining the reg property
with the register address and size at first index
followed by the external memory base address and max allocated
xspi1 is addressing max 256 MBytes from 0x90000000

Signed-off-by: Francois Ramu <francois.ramu@st.com>

Author: FRASTM

dts/arm/st/h5/stm32h562.dtsi

@@ -260,13 +260,13 @@
 
 		xspi1: spi@47001400 {
 			compatible = "st,stm32-xspi";
-			reg = <0x47001400 0x400>;
+			reg = <0x47001400 0x400>, <0x90000000 DT_SIZE_M(256)>;
 			interrupts = <78 0>;
 			clock-names = "xspix", "xspi-ker";
 			clocks = <&rcc STM32_CLOCK(AHB4, 20U)>,
 				<&rcc STM32_SRC_PLL1_Q OCTOSPI1_SEL(1)>;
 			#address-cells = <1>;
-			#size-cells = <1>;
+			#size-cells = <0>;
 			status = "disabled";
 		};