env_onenand: set ONENAND_MAX_ENV_SIZE to CONFIG_ENV_SIZE

This fix prevents env_import() CRC to fail when CONFIG_ENV_SIZE
is not equal to 4096 bytes
It also prevents mtd->read and mtd->write to be incomplete when
the environment is larger than 4096 bytes.

Signed-off-by: David du Colombier <0intro@gmail.com>

common/env_onenand.c

@@ -39,7 +39,7 @@
 
 char *env_name_spec = "OneNAND";
 
-#define ONENAND_MAX_ENV_SIZE	4096
+#define ONENAND_MAX_ENV_SIZE	CONFIG_ENV_SIZE
 #define ONENAND_ENV_SIZE(mtd)	(ONENAND_MAX_ENV_SIZE - ENV_HEADER_SIZE)
 
 DECLARE_GLOBAL_DATA_PTR;