samples: ipc: openamp: Fix missed return error check

The return from ipm_set_enabled wasn't assigned to 'status' so the check
right after the call to ipm_set_enabled() wasn't doing the right thing.

Fixes: #13881
Coverity CID: 190932

Signed-off-by: Kumar Gala <kumar.gala@linaro.org>

samples/subsys/ipc/openamp/src/main.c

@@ -200,7 +200,7 @@ void app_task(void *arg1, void *arg2, void *arg3)
 
 	ipm_register_callback(ipm_handle, platform_ipm_callback, NULL);
 
-	ipm_set_enabled(ipm_handle, 1);
+	status = ipm_set_enabled(ipm_handle, 1);
 	if (status != 0) {
 		printk("ipm_set_enabled failed\n");
 		return;