omap5912-osk: Increase flash partition for u-boot

The current u-boot binary needs more than 128KB of flash space and so
move the u-boot environment from an offset of 128KB to 256KB in flash
to ensure the enviroment does not overlap with u-boot.
Signed-off-by: NJon Hunter <jon-hunter@ti.com>

include/configs/omap5912osk.h

@@ -178,10 +178,10 @@
  */
 #define CONFIG_ENV_IS_IN_FLASH	1
 /* addr of environment */
-#define CONFIG_ENV_ADDR	(CONFIG_SYS_FLASH_BASE + 0x020000)
+#define CONFIG_ENV_ADDR	(CONFIG_SYS_FLASH_BASE + CONFIG_ENV_OFFSET)
 
 #define CONFIG_ENV_SIZE		0x20000	/* Total Size of Environment Sector */
-#define CONFIG_ENV_OFFSET	0x20000	/* environment starts here  */
+#define CONFIG_ENV_OFFSET	0x40000	/* environment starts here  */
 
 #define CONFIG_SYS_SDRAM_BASE		PHYS_SDRAM_1
 #define CONFIG_SYS_INIT_RAM_ADDR        PHYS_SRAM