mpc83xx: increase MONITOR_LEN to offset growing pains

Saving the environment leads to overwriting u-boot itself,
bricking boards.  Increase u-boot's image size so the environment
base address doesn't end up overlapping u-boot text.

Signed-off-by: Kim Phillips <kim.phillips@freescale.com>
diff --git a/include/configs/MPC837XERDB.h b/include/configs/MPC837XERDB.h
index 2b7d629..0205c99 100644
--- a/include/configs/MPC837XERDB.h
+++ b/include/configs/MPC837XERDB.h
@@ -228,7 +228,7 @@
 #undef	CONFIG_SYS_RAMBOOT
 #endif
 
-#define CONFIG_SYS_MONITOR_LEN		(256 * 1024) /* Reserve 256 kB for Mon */
+#define CONFIG_SYS_MONITOR_LEN		(384 * 1024) /* Reserve 384 kB for Mon */
 #define CONFIG_SYS_MALLOC_LEN		(512 * 1024) /* Reserved for malloc */
 
 /*