Use new-style return values from spci_msg_wait and spci_msg_poll.

Bug: 141469322
Change-Id: Ib9815695537837f029c698c6966bad93c094e89e
diff --git a/inc/hf/api.h b/inc/hf/api.h
index cc45a05..ebc6b20 100644
--- a/inc/hf/api.h
+++ b/inc/hf/api.h
@@ -56,7 +56,8 @@
 
 spci_return_t api_spci_msg_send(uint32_t attributes, struct vcpu *current,
 				struct vcpu **next);
-int32_t api_spci_msg_recv(bool block, struct vcpu *current, struct vcpu **next);
+struct spci_value api_spci_msg_recv(bool block, struct vcpu *current,
+				    struct vcpu **next);
 void api_yield(struct vcpu *current, struct vcpu **next);
 struct spci_value api_spci_version(void);
 spci_return_t api_spci_share_memory(struct vm_locked to_locked,