feat(intel): support ECDH request

This command sends the request on generating a share secret on
Diffie-Hellman key exchange.

Signed-off-by: Siew Chin Lim <elly.siew.chin.lim@intel.com>
Signed-off-by: Boon Khai Ng <boon.khai.ng@intel.com>
Signed-off-by: Sieu Mun Tang <sieu.mun.tang@intel.com>
Change-Id: Ic7c8470cf036ea8c17bf87401f49936950b3e1d6
diff --git a/plat/intel/soc/common/include/socfpga_mailbox.h b/plat/intel/soc/common/include/socfpga_mailbox.h
index 042532c..f2780c2 100644
--- a/plat/intel/soc/common/include/socfpga_mailbox.h
+++ b/plat/intel/soc/common/include/socfpga_mailbox.h
@@ -81,6 +81,7 @@
 #define MBOX_FCS_ECDSA_SHA2_DATA_SIGN_REQ		0x85
 #define MBOX_FCS_ECDSA_SHA2_DATA_SIGN_VERIFY		0x87
 #define MBOX_FCS_ECDSA_GET_PUBKEY			0x88
+#define MBOX_FCS_ECDH_REQUEST				0x89
 #define MBOX_FCS_OPEN_CS_SESSION			0xA0
 #define MBOX_FCS_CLOSE_CS_SESSION			0xA1
 #define MBOX_FCS_IMPORT_CS_KEY				0xA5