core: spmc: fix direct request handler

The FF-A direct request handling has an error: if the destination ID is
the SPMC ID, the handler is trying to forward the message to an SP with
this ID, which is obviously non-existent so this gives an error.

Fixes: 19ad526 ("core: spmc, sp: cleanup FF-A ID handling")
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>
Signed-off-by: Balint Dobszay <balint.dobszay@arm.com>

core/arch/arm/kernel/thread_spmc.c

@@ -836,6 +836,7 @@ static void handle_direct_request(struct thread_smc_args *args,
 	uint32_t direct_resp_fid = 0;
 
 	if (IS_ENABLED(CFG_SECURE_PARTITION) &&
+	    FFA_DST(args->a1) != spmc_id &&
 	    FFA_DST(args->a1) != optee_endpoint_id) {
 		spmc_sp_start_thread(args);
 		return;