kernel; Checking functions return

Checking the return of some scattered functions across kernel.
MISRA-C requires that all non-void functions have their return value
checked, though, in some cases there is nothing to do. Just
acknowledging it.

Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>

kernel/device.c

@@ -51,7 +51,7 @@ void _sys_device_do_config_level(int level)
 								info++) {
 		struct device_config *device = info->config;
 
-		device->init(info);
+		(void)device->init(info);
 		_k_object_init(info);
 	}
 }

kernel/mailbox.c

@@ -35,7 +35,7 @@ K_STACK_DEFINE(async_msg_free, CONFIG_NUM_MBOX_ASYNC_MSGS);
 /* allocate an asynchronous message descriptor */
 static inline void mbox_async_alloc(struct k_mbox_async **async)
 {
-	k_stack_pop(&async_msg_free, (u32_t *)async, K_FOREVER);
+	(void)k_stack_pop(&async_msg_free, (u32_t *)async, K_FOREVER);
 }
 
 /* free an asynchronous message descriptor */
@@ -332,7 +332,7 @@ void k_mbox_async_put(struct k_mbox *mbox, struct k_mbox_msg *tx_msg,
 	async->tx_msg._syncing_thread = (struct k_thread *)&async->thread;
 	async->tx_msg._async_sem = sem;
 
-	mbox_message_put(mbox, &async->tx_msg, K_FOREVER);
+	(void)mbox_message_put(mbox, &async->tx_msg, K_FOREVER);
 }
 #endif
 

kernel/pipes.c

@@ -54,7 +54,7 @@ K_STACK_DEFINE(pipe_async_msgs, CONFIG_NUM_PIPE_ASYNC_MSGS);
 /* Allocate an asynchronous message descriptor */
 static void pipe_async_alloc(struct k_pipe_async **async)
 {
-	k_stack_pop(&pipe_async_msgs, (u32_t *)async, K_FOREVER);
+	(void)k_stack_pop(&pipe_async_msgs, (u32_t *)async, K_FOREVER);
 }
 
 /* Free an asynchronous message descriptor */

kernel/smp.c

@@ -96,7 +96,7 @@ void smp_init(void)
 {
 	atomic_t start_flag;
 
-	atomic_clear(&start_flag);
+	(void)atomic_clear(&start_flag);
 
 #if defined(CONFIG_SMP) && CONFIG_MP_NUM_CPUS > 1
 	_arch_start_cpu(1, _interrupt_stack1, CONFIG_ISR_STACK_SIZE,
@@ -113,5 +113,5 @@ void smp_init(void)
 			smp_init_top, &start_flag);
 #endif
 
-	atomic_set(&start_flag, 1);
+	(void)atomic_set(&start_flag, 1);
 }