warp7: Fix U-Boot corruption after saving the environment

U-Boot binary has grown in such a way that it goes beyond the reserved
area for the environment variables.

Running "saveenv" followed by a "reset" causes U-Boot to hang because
of this overlap.

Fix this problem by increasing the CONFIG_ENV_OFFSET size.

Also, in order to prevent this same problem in the future, use
CONFIG_BOARD_SIZE_LIMIT, which will detect the overlap in build-time.

CONFIG_BOARD_SIZE_LIMIT does not accept math expressions, so declare
CONFIG_ENV_OFFSET with its direct value instead.

Signed-off-by: Fabio Estevam <festevam@gmail.com>
Acked-by: Pierre-Jean Texier <pjtexier@koncepto.io>
Tested-by: Pierre-Jean Texier <pjtexier@koncepto.io>
Acked-by: Joris Offouga <offougajoris@gmail.com>
Tested-by: Joris Offouga <offougajoris@gmail.com>
diff --git a/include/configs/warp7.h b/include/configs/warp7.h
index 9a82581..da894ec 100644
--- a/include/configs/warp7.h
+++ b/include/configs/warp7.h
@@ -125,6 +125,19 @@
 #define CONFIG_SYS_INIT_SP_ADDR \
 	(CONFIG_SYS_INIT_RAM_ADDR + CONFIG_SYS_INIT_SP_OFFSET)
 
+/*
+ * Environment starts at CONFIG_ENV_OFFSET= 0xC0000 = 768k = 768*1024 = 786432
+ *
+ * Detect overlap between U-Boot image and environment area in build-time
+ *
+ * CONFIG_BOARD_SIZE_LIMIT = CONFIG_ENV_OFFSET - u-boot.imx offset
+ * CONFIG_BOARD_SIZE_LIMIT = 768k - 1k = 767k = 785408
+ *
+ * Currently CONFIG_BOARD_SIZE_LIMIT does not handle expressions, so
+ * write the direct value here
+ */
+#define CONFIG_BOARD_SIZE_LIMIT		785408
+
 /* I2C configs */
 #define CONFIG_SYS_I2C_MXC
 #define CONFIG_SYS_I2C_SPEED		100000