imx: mx6: Change ENV offset to 512K bytes for larger u-boot image

To align with other mx6 boards, change ENV offset from 384KB to
512KB position to fit a larger u-boot image.

Signed-off-by: Ye.Li <B37916@freescale.com>
diff --git a/include/configs/mx6sxsabresd.h b/include/configs/mx6sxsabresd.h
index 54cdd64..404b922 100644
--- a/include/configs/mx6sxsabresd.h
+++ b/include/configs/mx6sxsabresd.h
@@ -260,7 +260,7 @@
 #define FSL_QSPI_FLASH_NUM		2
 #endif
 
-#define CONFIG_ENV_OFFSET		(6 * SZ_64K)
+#define CONFIG_ENV_OFFSET		(8 * SZ_64K)
 #define CONFIG_ENV_SIZE			SZ_8K
 #define CONFIG_ENV_IS_IN_MMC