arm: zynq: Make ENV_SIZE and ENV_OFFSET optional via board file

Boards have an option to rewrite variable locations in their own board
files. This is necessary for qspi and nand configurations where boot
image can be bigger then 896k(current limit).
Signed-off-by: NMichal Simek <michal.simek@xilinx.com>

include/configs/zynq-common.h

@@ -127,7 +127,9 @@
 #endif
 
 /* Total Size of Environment Sector */
-#define CONFIG_ENV_SIZE			(128 << 10)
+#ifndef CONFIG_ENV_SIZE
+# define CONFIG_ENV_SIZE			(128 << 10)
+#endif
 
 /* Allow to overwrite serial and ethaddr */
 #define CONFIG_ENV_OVERWRITE
@@ -135,7 +137,9 @@
 /* Environment */
 #ifndef CONFIG_ENV_IS_NOWHERE
 # define CONFIG_ENV_SECT_SIZE		CONFIG_ENV_SIZE
-# define CONFIG_ENV_OFFSET		0xE0000
+# ifndef CONFIG_ENV_OFFSET
+#  define CONFIG_ENV_OFFSET		0xE0000
+# endif
 #endif
 
 /* enable preboot to be loaded before CONFIG_BOOTDELAY */