ARM: dts: meson: add a node which describes the SRAM

All 32bit Meson SoCs contain 128KiB SRAM. This SRAM is used when
suspending the device (the the ARM Power Firmware on
Meson8/Meson8b/Meson8m2 saves the DDR settings there) and to boot the
secondary CPU cores.
Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Signed-off-by: Kevin Hilman <khilman@baylibre.com>

arch/arm/boot/dts/meson.dtsi

@@ -244,5 +244,13 @@ ethmac: ethernet@c9410000 {
 			interrupt-names = "macirq";
 			status = "disabled";
 		};
+
+		ahb_sram: sram@d9000000 {
+			compatible = "mmio-sram";
+			reg = <0xd9000000 0x20000>;
+			#address-cells = <1>;
+			#size-cells = <1>;
+			ranges = <0 0xd9000000 0x20000>;
+		};
 	};
 }; /* end of / */