ot1200: make use of imx_ddr_size(..)

To support different ddr3 memory sizes we should start using
imx_ddr_size(..) instead of the define PHYS_SDRAM_SIZE.

Signed-off-by: Christian Gmeiner <christian.gmeiner@gmail.com>
diff --git a/board/bachmann/ot1200/ot1200.c b/board/bachmann/ot1200/ot1200.c
index 93f3d65..039e858 100644
--- a/board/bachmann/ot1200/ot1200.c
+++ b/board/bachmann/ot1200/ot1200.c
@@ -16,6 +16,7 @@
 #include <asm/imx-common/mxc_i2c.h>
 #include <asm/imx-common/boot_mode.h>
 #include <asm/arch/crm_regs.h>
+#include <asm/arch/sys_proto.h>
 #include <mmc.h>
 #include <fsl_esdhc.h>
 #include <netdev.h>
@@ -46,7 +47,7 @@
 
 int dram_init(void)
 {
-	gd->ram_size = get_ram_size((void *)PHYS_SDRAM, PHYS_SDRAM_SIZE);
+	gd->ram_size = imx_ddr_size();
 
 	return 0;
 }