sunxi: Add limit with the MMC environment

The MMC environment offset is getting very close to the end of the U-Boot
binary now. Since we want to make sure this will not overflow, add a size
limit in the board for arm64. arm32 has already that limit enforced in our
custom image generation.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Jagan Teki <jagan@openedev.com>

include/configs/sunxi-common.h

@@ -147,6 +147,16 @@
 #endif
 
 #if defined(CONFIG_ENV_IS_IN_MMC)
+
+#ifdef CONFIG_ARM64
+/*
+ * This is actually (CONFIG_ENV_OFFSET -
+ * (CONFIG_SYS_MMCSD_RAW_MODE_U_BOOT_SECTOR * 512)), but the value will be used
+ * directly in a makefile, without the preprocessor expansion.
+ */
+#define CONFIG_BOARD_SIZE_LIMIT		0x7e000
+#endif
+
 #if CONFIG_MMC_SUNXI_SLOT_EXTRA != -1
 /* If we have two devices (most likely eMMC + MMC), favour the eMMC */
 #define CONFIG_SYS_MMC_ENV_DEV		1