fix(intel): define macros to handle buffer entries

This patch defines a macro to handle Secure Device Manager's (SDM)
pointer to command & response buffer entries and convert them to the
correct physical address.

Signed-off-by: Abdul Halim, Muhammad Hadi Asyrafi <muhammad.hadi.asyrafi.abdul.halim@intel.com>
Change-Id: I4cf9f1d90e0d5ae4e1a2ce84165864b48c2862e7
diff --git a/plat/intel/soc/common/include/socfpga_mailbox.h b/plat/intel/soc/common/include/socfpga_mailbox.h
index 923c4f1..27f8277 100644
--- a/plat/intel/soc/common/include/socfpga_mailbox.h
+++ b/plat/intel/soc/common/include/socfpga_mailbox.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019-2020, Intel Corporation. All rights reserved.
+ * Copyright (c) 2019-2022, Intel Corporation. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -69,6 +69,7 @@
 #define CMD_CASUAL			0
 #define CMD_URGENT			1
 
+#define MBOX_WORD_BYTE			4U
 #define MBOX_RESP_BUFFER_SIZE		16
 #define MBOX_CMD_BUFFER_SIZE		32
 
@@ -108,6 +109,9 @@
 
 /* Mailbox Macros */
 
+#define MBOX_ENTRY_TO_ADDR(_buf, ptr)	(MBOX_OFFSET + (MBOX_##_buf##_BUFFER) \
+						+ MBOX_WORD_BYTE * (ptr))
+
 /* Mailbox interrupt flags and masks */
 #define MBOX_INT_FLAG_COE		0x1
 #define MBOX_INT_FLAG_RIE		0x2