qemu-arm: Add persistent environment support

Currently on qemu-arm platforms environment is kept in RAM. Instead
use pflash device 1 to provide persistent environment support across
device reset.

Also (optionally) provide support for persistent environment across
qemu machine OFF/ON using following instructions:

- Create envstore.img using qemu-img:
    qemu-img create -f raw envstore.img 64M
- Add a pflash drive parameter to the command line:
    -drive if=pflash,format=raw,index=1,file=envstore.img

Signed-off-by: Sumit Garg <sumit.garg@linaro.org>

include/configs/qemu-arm.h

@@ -21,7 +21,8 @@
 #define CONFIG_SYS_HZ                       1000
 
 /* Environment options */
-#define CONFIG_ENV_SIZE				SZ_64K
+#define CONFIG_ENV_ADDR			0x4000000
+#define CONFIG_ENV_SIZE			SZ_256K
 
 #define BOOT_TARGET_DEVICES(func) \
 	func(SCSI, scsi, 0) \
@@ -43,4 +44,9 @@
 
 #define CONFIG_SYS_CBSIZE 512
 
+#define CONFIG_SYS_MONITOR_BASE		CONFIG_SYS_TEXT_BASE
+#define CONFIG_SYS_FLASH_BASE		0x0
+#define CONFIG_SYS_MAX_FLASH_BANKS	2
+#define CONFIG_SYS_MAX_FLASH_SECT	256 /* Sector: 256K, Bank: 64M */
+
 #endif /* __CONFIG_H */