arm: mvebu: clearfog: fix boot from SD card

Enable gpio0 in SPL to allow the sdhci driver read the SD card-detect
signal.
Signed-off-by: NBaruch Siach <baruch@tkos.co.il>
Reviewed-by: NStefan Roese <sr@denx.de>

arch/arm/dts/armada-388-clearfog-u-boot.dtsi

@@ -12,6 +12,10 @@
 	u-boot,dm-spl;
 };
 
+&gpio0 {
+	u-boot,dm-spl;
+};
+
 &ahci0 {
 	u-boot,dm-spl;
 };