coding guidelines: comply with MISRA Rule 21.15

- made explicit the copied data type

Signed-off-by: Hess Nathan <nhess@baumer.com>

kernel/msg_q.c

@@ -151,7 +151,7 @@ int z_impl_k_msgq_put(struct k_msgq *msgq, const void *data, k_timeout_t timeout
 			/* put message in queue */
 			__ASSERT_NO_MSG(msgq->write_ptr >= msgq->buffer_start &&
 					msgq->write_ptr < msgq->buffer_end);
-			(void)memcpy(msgq->write_ptr, data, msgq->msg_size);
+			(void)memcpy(msgq->write_ptr, (char *)data, msgq->msg_size);
 			msgq->write_ptr += msgq->msg_size;
 			if (msgq->write_ptr == msgq->buffer_end) {
 				msgq->write_ptr = msgq->buffer_start;
@@ -227,7 +227,7 @@ int z_impl_k_msgq_get(struct k_msgq *msgq, void *data, k_timeout_t timeout)
 
 	if (msgq->used_msgs > 0U) {
 		/* take first available message from queue */
-		(void)memcpy(data, msgq->read_ptr, msgq->msg_size);
+		(void)memcpy((char *)data, msgq->read_ptr, msgq->msg_size);
 		msgq->read_ptr += msgq->msg_size;
 		if (msgq->read_ptr == msgq->buffer_end) {
 			msgq->read_ptr = msgq->buffer_start;
@@ -242,7 +242,7 @@ int z_impl_k_msgq_get(struct k_msgq *msgq, void *data, k_timeout_t timeout)
 			/* add thread's message to queue */
 			__ASSERT_NO_MSG(msgq->write_ptr >= msgq->buffer_start &&
 					msgq->write_ptr < msgq->buffer_end);
-			(void)memcpy(msgq->write_ptr, pending_thread->base.swap_data,
+			(void)memcpy(msgq->write_ptr, (char *)pending_thread->base.swap_data,
 			       msgq->msg_size);
 			msgq->write_ptr += msgq->msg_size;
 			if (msgq->write_ptr == msgq->buffer_end) {
@@ -302,7 +302,7 @@ int z_impl_k_msgq_peek(struct k_msgq *msgq, void *data)
 
 	if (msgq->used_msgs > 0U) {
 		/* take first available message from queue */
-		(void)memcpy(data, msgq->read_ptr, msgq->msg_size);
+		(void)memcpy((char *)data, msgq->read_ptr, msgq->msg_size);
 		result = 0;
 	} else {
 		/* don't wait for a message to become available */