lorawan: always wait for MAC ops to complete

Wait for MAC operations to complete when transmitting. Unconfirmed
messages still open receive windows and can cause error conditions,
which are currently dropped.

It is also possible for a second send to be requested before the first
one has finished processing, which results in `LORAMAC_STATUS_BUSY`.
Empty frames (due to insufficient payload space) now also block until
the MAC layer is ready to accept new commands.

This change means the application no longer needs to guess-and-check
when it is possible to send unconfirmed messages.

Fixes #33456.

Signed-off-by: Jordan Yates <jordan.yates@data61.csiro.au>

subsys/lorawan/lorawan.c

@@ -124,10 +124,7 @@ static void McpsConfirm(McpsConfirm_t *mcpsConfirm)
 	}
 
 	last_mcps_confirm_status = mcpsConfirm->Status;
-	/* mcps_confirm_sem is only blocked on in the MCPS_CONFIRMED case */
-	if (mcpsConfirm->McpsRequest == MCPS_CONFIRMED) {
-		k_sem_give(&mcps_confirm_sem);
-	}
+	k_sem_give(&mcps_confirm_sem);
 }
 
 static void McpsIndication(McpsIndication_t *mcpsIndication)
@@ -492,26 +489,22 @@ int lorawan_send(uint8_t port, uint8_t *data, uint8_t len, uint8_t flags)
 	}
 
 	/*
-	 * Indicate to the application that the current packet is not sent and
+	 * Always wait for MAC operations to complete.
+	 * We can be sure that the semaphore will be released for
+	 * both success and failure cases after a specific time period.
+	 * So we can use K_FOREVER and no need to check the return val.
+	 */
+	k_sem_take(&mcps_confirm_sem, K_FOREVER);
+	if (last_mcps_confirm_status != LORAMAC_EVENT_INFO_STATUS_OK) {
+		ret = lorawan_eventinfo2errno(last_mcps_confirm_status);
+	}
+
+	/*
+	 * Indicate to the application that the provided data was not sent and
 	 * it has to resend the packet.
 	 */
 	if (empty_frame) {
 		ret = -EAGAIN;
-		goto out;
-	}
-
-	/* Wait for send confirmation */
-	if (flags & LORAWAN_MSG_CONFIRMED) {
-		/*
-		 * We can be sure that the semaphore will be released for
-		 * both success and failure cases after a specific time period.
-		 * So we can use K_FOREVER and no need to check the return val.
-		 */
-		k_sem_take(&mcps_confirm_sem, K_FOREVER);
-
-		if (last_mcps_confirm_status != LORAMAC_EVENT_INFO_STATUS_OK) {
-			ret = lorawan_eventinfo2errno(last_mcps_confirm_status);
-		}
 	}
 
 out: