fix(imx8m): backup mr12/14 value from lpddr4 chip

Backup the mr12/14 value as the actual value used is not the
one we configured in the ddrc config timing.

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Reviewed-by: Ye Li <ye.li@nxp.com>
Change-Id: If04733b34a3b4c080828bb7c82e83f0badbeaafd
diff --git a/plat/imx/imx8m/include/dram.h b/plat/imx/imx8m/include/dram.h
index e8caa21..719c390 100644
--- a/plat/imx/imx8m/include/dram.h
+++ b/plat/imx/imx8m/include/dram.h
@@ -23,6 +23,9 @@
 #define DDRC_ACTIVE_ONE_RANK	U(0x1)
 #define DDRC_ACTIVE_TWO_RANK	U(0x2)
 
+#define MR12			U(12)
+#define MR14			U(14)
+
 #define MAX_FSP_NUM		U(3)
 
 /* reg & config param */