ARC: HSDK: Enable SPI flash support

HSDK board has sst26wf016 SPI flash IC which we want to support.

Add SPI controller, CS-gpio and SPI flash nodes to hsdk device tree.
Enable corresponding options in hsdk defconfig.

For SPI write functionality to work we need [1] which
adds support of sst26xxx ICs.

[1] https://patchwork.ozlabs.org/project/uboot/list/?series=35796

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
diff --git a/arch/arc/dts/hsdk.dts b/arch/arc/dts/hsdk.dts
index 09f3fe9..80b864a 100644
--- a/arch/arc/dts/hsdk.dts
+++ b/arch/arc/dts/hsdk.dts
@@ -14,6 +14,7 @@
 
 	aliases {
 		console = &uart0;
+		spi0 = &spi0;
 	};
 
 	cpu_card {
@@ -83,4 +84,29 @@
 		compatible = "generic-ohci";
 		reg = <0xf0060000 0x100>;
 	};
+
+	spi0: spi@f0020000 {
+		compatible = "snps,dw-apb-ssi";
+		reg = <0xf0020000 0x1000>;
+		#address-cells = <1>;
+		#size-cells = <0>;
+		spi-max-frequency = <4000000>;
+		clocks = <&cgu_clk CLK_SYS_SPI_REF>;
+		clock-names = "spi_clk";
+		cs-gpio = <&cs_gpio 0>;
+		spi_flash@0 {
+			compatible = "spi-flash";
+			reg = <0>;
+			spi-max-frequency = <4000000>;
+		};
+	};
+
+	cs_gpio: gpio@f00014b0 {
+		compatible = "snps,hsdk-creg-gpio";
+		reg = <0xf00014b0 0x4>;
+		gpio-controller;
+		#gpio-cells = <1>;
+		gpio-bank-name = "hsdk-spi-cs";
+		gpio-count = <1>;
+	};
 };