feat: allow an endpoint to specify optional timeout with FFA_YIELD

An endpoint can yield execution back to the VM that allocated it CPU
cycles rather than busy waiting (such as for an IO operation to
 complete). FF-A v1.2 spec allows the endpoint to specify an optional
64-bit timeout.

Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
Change-Id: I5481c5483f4edd71b95c15a11a118498c71e3fa1
diff --git a/inc/hf/api.h b/inc/hf/api.h
index f3b8eea..660a1c3 100644
--- a/inc/hf/api.h
+++ b/inc/hf/api.h
@@ -62,7 +62,8 @@
 				  uint32_t page_count, struct vcpu *current);
 struct ffa_value api_ffa_rxtx_unmap(ffa_vm_id_t allocator_id,
 				    struct vcpu *current);
-struct ffa_value api_yield(struct vcpu *current, struct vcpu **next);
+struct ffa_value api_yield(struct vcpu *current, struct vcpu **next,
+			   struct ffa_value *args);
 struct ffa_value api_ffa_version(struct vcpu *current,
 				 uint32_t requested_version);
 struct ffa_value api_ffa_partition_info_get(struct vcpu *current,