ath10k: don't use return on void functions

Fixes a checkpatch warning:

WARNING: void function return statements are not generally useful

Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>
diff --git a/drivers/net/wireless/ath/ath10k/htt_tx.c b/drivers/net/wireless/ath/ath10k/htt_tx.c
index 1ab6463..bd87a35 100644
--- a/drivers/net/wireless/ath/ath10k/htt_tx.c
+++ b/drivers/net/wireless/ath/ath10k/htt_tx.c
@@ -154,7 +154,6 @@
 	kfree(htt->pending_tx);
 	kfree(htt->used_msdu_ids);
 	dma_pool_destroy(htt->tx_pool);
-	return;
 }
 
 void ath10k_htt_htc_tx_complete(struct ath10k *ar, struct sk_buff *skb)