axs10x: Move environment from I2C EEPROM to SD-card

With deprecation of I2C EEPROM we we left without a permamnent
storage for U-Boot environment, but luckily we may simply use SD-card
with FAT partition for that.

Having environment on SD-card is much more convenient as it
allows us to preserve all the settings when moving from one board to
another. Moreover instead of 256 bytes of EEPROM we're now virtually
unlimited in stuff being placed in environment like complicated scripts
etc which are usually required in case of full-scale distros.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

include/configs/axs10x.h

@@ -75,9 +75,12 @@
 /*
  * Environment settings
  */
-#define CONFIG_ENV_IS_NOWHERE
-#define CONFIG_ENV_SIZE			SZ_512
-#define CONFIG_ENV_OFFSET		0
+#define CONFIG_ENV_IS_IN_FAT
+#define CONFIG_ENV_SIZE			SZ_16K
+#define FAT_ENV_INTERFACE		"mmc"
+#define FAT_ENV_DEVICE_AND_PART		"0:1"
+#define FAT_ENV_FILE			"uboot.env"
+#define CONFIG_FAT_WRITE
 
 /*
  * Environment configuration