Use 64-bit calling convention for function with 64-bit addresses.

Change-Id: If19970fdee75518e9ce91f34bb4b1186224472a3
diff --git a/inc/vmapi/hf/spci.h b/inc/vmapi/hf/spci.h
index a70dcdd..c7638ce 100644
--- a/inc/vmapi/hf/spci.h
+++ b/inc/vmapi/hf/spci.h
@@ -33,6 +33,7 @@
 #define SPCI_FEATURES_32              0x84000064
 #define SPCI_RX_RELEASE_32            0x84000065
 #define SPCI_RXTX_MAP_32              0x84000066
+#define SPCI_RXTX_MAP_64              0xC4000066
 #define SPCI_RXTX_UNMAP_32            0x84000067
 #define SPCI_PARTITION_INFO_GET_32    0x84000068
 #define SPCI_ID_GET_32                0x84000069