arm: add Cubieboard7 board support

The Cubieboard is a single board computer containing a
Actions S700 SoC(with 4 ARMv8 Cortex-A53 cores).

This patch adds respective defconfig alongwith .dts(copied
from Linux v5.5-rc6 with hash "b3a987b0264d").
Signed-off-by: NAmit Singh Tomar <amittomer25@gmail.com>

arch/arm/dts/s700-cubieboard7.dts

+// SPDX-License-Identifier: (GPL-2.0+ OR MIT)
+/*
+ * Copyright (c) 2017 Andreas Färber
+ */
+
+/dts-v1/;
+
+#include "s700.dtsi"
+
+/ {
+	compatible = "cubietech,cubieboard7", "actions,s700";
+	model = "CubieBoard7";
+
+	aliases {
+		serial3 = &uart3;
+	};
+
+	chosen {
+		stdout-path = "serial3:115200n8";
+	};
+
+	memory@0 {
+		device_type = "memory";
+		reg = <0x0 0x0 0x0 0x80000000>;
+	};
+
+	memory@1,e0000000 {
+		device_type = "memory";
+		reg = <0x1 0xe0000000 0x0 0x0>;
+	};
+};
+
+&i2c0 {
+	status = "okay";
+	pinctrl-names = "default";
+	pinctrl-0 = <&i2c0_default>;
+};
+
+&i2c1 {
+	status = "okay";
+	pinctrl-names = "default";
+	pinctrl-0 = <&i2c1_default>;
+};
+
+&i2c2 {
+	status = "disabled";
+	pinctrl-names = "default";
+	pinctrl-0 = <&i2c2_default>;
+};
+
+&pinctrl {
+	i2c0_default: i2c0_default {
+		pinmux {
+			groups = "i2c0_mfp";
+			function = "i2c0";
+		};
+		pinconf {
+			pins = "i2c0_sclk", "i2c0_sdata";
+			bias-pull-up;
+		};
+	};
+
+	i2c1_default: i2c1_default {
+		pinmux {
+			groups = "i2c1_dummy";
+			function = "i2c1";
+		};
+		pinconf {
+			pins = "i2c1_sclk", "i2c1_sdata";
+			bias-pull-up;
+		};
+	};
+
+	i2c2_default: i2c2_default {
+		pinmux {
+			groups = "i2c2_dummy";
+			function = "i2c2";
+		};
+		pinconf {
+			pins = "i2c2_sclk", "i2c2_sdata";
+			bias-pull-up;
+		};
+	};
+};
+
+&timer {
+	clocks = <&hosc>;
+};
+
+&uart3 {
+	status = "okay";
+};

configs/cubieboard7_defconfig

+CONFIG_ARM=y
+CONFIG_ARCH_OWL=y
+CONFIG_MACH_S700=y
+CONFIG_IDENT_STRING="\ncubieboard7"
+CONFIG_DISTRO_DEFAULTS=y
+CONFIG_BOOTDELAY=5
+CONFIG_USE_BOOTARGS=y
+CONFIG_BOOTARGS="console=ttyOWL3,115200n8"
+# CONFIG_DISPLAY_CPUINFO is not set
+# CONFIG_DISPLAY_BOARDINFO is not set
+CONFIG_SYS_PROMPT="U-Boot => "
+CONFIG_DEFAULT_DEVICE_TREE="s700-cubieboard7"