Fix register usage of SPCI_SUCCESS.

Change-Id: Iab5b5d2a5f98a069d90a09d721c1d66a9f142994
diff --git a/src/api.c b/src/api.c
index 5261688..92328c8 100644
--- a/src/api.c
+++ b/src/api.c
@@ -1677,7 +1677,7 @@
 
 	struct spci_value ret = {
 		.func = SPCI_SUCCESS_32,
-		.arg1 = (SPCI_VERSION_MAJOR << SPCI_VERSION_MAJOR_OFFSET) |
+		.arg2 = (SPCI_VERSION_MAJOR << SPCI_VERSION_MAJOR_OFFSET) |
 			SPCI_VERSION_MINOR};
 	return ret;
 }
diff --git a/test/vmapi/primary_only/primary_only.c b/test/vmapi/primary_only/primary_only.c
index 45fce1d..96b1309 100644
--- a/test/vmapi/primary_only/primary_only.c
+++ b/test/vmapi/primary_only/primary_only.c
@@ -155,7 +155,7 @@
 
 	struct spci_value ret = spci_version();
 	EXPECT_EQ(ret.func, SPCI_SUCCESS_32);
-	EXPECT_EQ(ret.arg1, current_version);
+	EXPECT_EQ(ret.arg2, current_version);
 }
 
 /**