MPC86xx: set CONFIG_MAX_MEM_MAPPED to 2G by default

Currently, we get 256MB as the default, but since all the 86xx
board configs define a 2G BAT mapping for RAM, raise default
to 2G.
Signed-off-by: NBecky Bruce <beckyb@kernel.crashing.org>
Acked-by: NJon Loeliger <jdl@freescale.com>

include/asm-ppc/config.h

@@ -22,7 +22,7 @@
 #define _ASM_CONFIG_H_
 
 #ifndef CONFIG_MAX_MEM_MAPPED
-#if defined(CONFIG_4xx) || defined(CONFIG_E500)
+#if defined(CONFIG_4xx) || defined(CONFIG_E500) || defined(CONFIG_MPC86xx)
 #define CONFIG_MAX_MEM_MAPPED	((phys_size_t)2 << 30)
 #else
 #define CONFIG_MAX_MEM_MAPPED	(256 << 20)