powerpc: mpc8548cds: extend the reserved length for monitor

Extend the reserved length for monitor to fix the following
build error:

BINMAN  u-boot-with-dtb.bin
Wrote map file './image.map' to show errors
binman: Section '/binman': contents size 0x80000 (524288)
exceeds section size 0x40000 (262144)
Makefile:1373: recipe for target 'u-boot-with-dtb.bin' failed
make: *** [u-boot-with-dtb.bin] Error 1

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Reviewed-by: Prabhakar Kushwaha <prabhakar.kushwaha@nxp.com>
diff --git a/include/configs/MPC8548CDS.h b/include/configs/MPC8548CDS.h
index b37601c..e2d6350 100644
--- a/include/configs/MPC8548CDS.h
+++ b/include/configs/MPC8548CDS.h
@@ -289,7 +289,7 @@
 #define CONFIG_SYS_GBL_DATA_OFFSET	(CONFIG_SYS_INIT_RAM_SIZE - GENERATED_GBL_DATA_SIZE)
 #define CONFIG_SYS_INIT_SP_OFFSET	CONFIG_SYS_GBL_DATA_OFFSET
 
-#define CONFIG_SYS_MONITOR_LEN		(256 * 1024) /* Reserve 256 kB for Mon */
+#define CONFIG_SYS_MONITOR_LEN		(512 * 1024)
 #define CONFIG_SYS_MALLOC_LEN	(1024 * 1024)	/* Reserved for malloc */
 
 /* Serial Port */