x86: adjust ramdisk load address

By default, ramdisk load address is defined to 02000000 in env string.
When loading bzImage to 01000000 (default address), there's a chance that
the ramdisk header would be overwritten by the kernel. Thus increase the
gap and make ramdisk load at 04000000 by default and also this patch
introduces a new configuration item CONFIG_RAMDISK_ADDR for this purpose

Signed-off-by: Miao Yan <yanmiaobest@gmail.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

include/configs/x86-common.h

@@ -208,6 +208,7 @@
 #define CONFIG_HOSTNAME		x86
 #define CONFIG_BOOTFILE		"bzImage"
 #define CONFIG_LOADADDR		0x1000000
+#define CONFIG_RAMDISK_ADDR		0x4000000
 
 #define CONFIG_EXTRA_ENV_SETTINGS			\
 	CONFIG_STD_DEVICES_SETTINGS			\
@@ -215,7 +216,7 @@
 	"netdev=eth0\0"					\
 	"consoledev=ttyS0\0"				\
 	"othbootargs=acpi=off\0"			\
-	"ramdiskaddr=0x2000000\0"			\
+	"ramdiskaddr=0x4000000\0"			\
 	"ramdiskfile=initramfs.gz\0"
 
 #define CONFIG_RAMBOOTCOMMAND				\