refactor(imx8m): replace magic number with enum type

Replace those RDC config related magic numbers with enum type

Signed-off-by: Jacky Bai <ping.bai@nxp.com>
Change-Id: I6245ccfa74d079179dc0f205980c2daf5c7af786
diff --git a/plat/imx/imx8m/include/imx_rdc.h b/plat/imx/imx8m/include/imx_rdc.h
index e25b0e6..a6e10a7 100644
--- a/plat/imx/imx8m/include/imx_rdc.h
+++ b/plat/imx/imx8m/include/imx_rdc.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019, NXP. All rights reserved.
+ * Copyright (c) 2019-2022 NXP. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -9,6 +9,7 @@
 
 #include <lib/utils_def.h>
 
+#include <imx_sec_def.h>
 #include <platform_def.h>
 
 #define MDAn(x)		(IMX_RDC_BASE + 0x200 + (x) * 4)