arm64: mvebu: armada-8k: support environment in SD/eMMC

Detect the SD/eMMC boot device at run-time. Load the environment from
the boot deice, as well as save to it.

Leave the environment offset the same as in the SPI flash.

Make SD/eMMC 0 the default environment device when the boot device is
not detected.

Cc: Konstantin Porotchkin <kostap@marvell.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/include/configs/mvebu_armada-8k.h b/include/configs/mvebu_armada-8k.h
index 93c5048..a6636e1 100644
--- a/include/configs/mvebu_armada-8k.h
+++ b/include/configs/mvebu_armada-8k.h
@@ -64,6 +64,9 @@
 #define CONFIG_ENV_SIZE			(64 << 10) /* 64KiB */
 #define CONFIG_ENV_SECT_SIZE		(64 << 10) /* 64KiB sectors */
 
+/* When runtime detection fails this is the default */
+#define CONFIG_SYS_MMC_ENV_DEV		0
+
 #define CONFIG_SYS_MAX_NAND_DEVICE	1
 #define CONFIG_SYS_NAND_MAX_CHIPS	1
 #define CONFIG_SYS_NAND_ONFI_DETECTION