arm: mvebu: helios4: Enable SPI flash support

Enable SPI flash support under U-Boot and SPL. The ENV size and offset,
ported from U-Boot 2013.01 Marvell version: 2015_T1.0p16

To create U-Boot image for SPI flash, user would need to replace
* CONFIG_MVEBU_SPL_BOOT_DEVICE_MMC with CONFIG_MVEBU_SPL_BOOT_DEVICE_SPI
* CONFIG_ENV_IS_IN_MMC with CONFIG_ENV_IS_IN_SPI_FLASH

Signed-off-by: Aditya Prayoga <aditya@kobol.io>
Reviewed-by: Stefan Roese <sr@denx.de>
Tested-By: Dennis Gilmore <dgilmore@redhat.com>
Reviewed-By: Dennis Gilmore <dgilmore@redhat.com>
Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/arch/arm/dts/armada-388-helios4-u-boot.dtsi b/arch/arm/dts/armada-388-helios4-u-boot.dtsi
index bd8c6ce..4bc00ae 100644
--- a/arch/arm/dts/armada-388-helios4-u-boot.dtsi
+++ b/arch/arm/dts/armada-388-helios4-u-boot.dtsi
@@ -4,5 +4,15 @@
 	aliases {
 		i2c0 = &i2c0;
 		i2c1 = &i2c1;
+		spi1 = &spi1;
 	};
 };
+
+&spi1 {
+	u-boot,dm-spl;
+};
+
+&w25q32 {
+	status = "okay";
+	u-boot,dm-spl;
+};