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

Change-Id: If19970fdee75518e9ce91f34bb4b1186224472a3
diff --git a/inc/vmapi/hf/call.h b/inc/vmapi/hf/call.h
index eec0df6..5a1e097 100644
--- a/inc/vmapi/hf/call.h
+++ b/inc/vmapi/hf/call.h
@@ -97,7 +97,7 @@
 					      hf_ipaddr_t recv)
 {
 	return spci_call(
-		(struct spci_value){.func = SPCI_RXTX_MAP_32,
+		(struct spci_value){.func = SPCI_RXTX_MAP_64,
 				    .arg1 = send,
 				    .arg2 = recv,
 				    .arg3 = HF_MAILBOX_SIZE / SPCI_PAGE_SIZE});