4xx: add missing CONFIG_SYS_SRAM_SIZE definition

A number of boards define CONFIG_SYS_SRAM_BASE but fail to define
CONFIG_SYS_SRAM_SIZE which is needed when cleaning up the code that
prints this information with the bdinfo command.

Add the missing deinitions.

Signed-off-by: Wolfgang Denk <wd@denx.de>
Cc: Stefan Roese <sr@denx.de>
Acked-by: Stefan Roese <sr@denx.de>
diff --git a/include/configs/bubinga.h b/include/configs/bubinga.h
index 627060a..159a265 100644
--- a/include/configs/bubinga.h
+++ b/include/configs/bubinga.h
@@ -179,6 +179,7 @@
  * (Set up by the startup code)
  */
 #define CONFIG_SYS_SRAM_BASE		0xFFF00000
+#define CONFIG_SYS_SRAM_SIZE		(256 << 10)
 #define CONFIG_SYS_FLASH_BASE		0xFFF80000
 
 /*-----------------------------------------------------------------------