ARC: [plat-hsdk]: Enable on-board SPI NOR flash IC

HSDK board has sst26wf016b SPI NOR flash IC installed, enable it.

Acked-by: Alexey Brodkin <[e-mail]>
Signed-off-by: Eugeniy Paltsev <[e-mail]>
Signed-off-by: Vineet Gupta <[e-mail]>

arch/arc/boot/dts/hsdk.dts

···
 			clocks = <&input_clk>;
 			cs-gpios = <&creg_gpio 0 GPIO_ACTIVE_LOW>,
 				   <&creg_gpio 1 GPIO_ACTIVE_LOW>;
+
+			spi-flash@0 {
+				compatible = "sst26wf016b", "jedec,spi-nor";
+				reg = <0>;
+				#address-cells = <1>;
+				#size-cells = <1>;
+				spi-max-frequency = <4000000>;
+			};
 		};
 
 		creg_gpio: gpio@14b0 {

arch/arc/configs/hsdk_defconfig

···
 CONFIG_DEVTMPFS=y
 # CONFIG_STANDALONE is not set
 # CONFIG_PREVENT_FIRMWARE_BUILD is not set
+CONFIG_MTD=y
+CONFIG_MTD_SPI_NOR=y
 CONFIG_SCSI=y
 CONFIG_BLK_DEV_SD=y
 CONFIG_NETDEVICES=y