qcacld-3.0: Sanity check on tx len before sending

Check length of the data passed in the hw tx desc and
assert it is not zero-length.
This will make it then easy to debug it on host side.

Change-Id: I7d77ac5ee6f5a4992c4a91b9d5661d207732862f
CRs-Fixed: 2136638

core/dp/htt/htt_tx.c

@@ -1782,6 +1782,8 @@ htt_tx_desc_init(htt_pdev_handle pdev,
 		HTT_TX_DESC_FRM_LEN_SET(local_word1, qdf_nbuf_len(msdu));
 	}
 
+	QDF_BUG(HTT_TX_DESC_FRM_LEN_GET(local_word1) != 0);
+
 	HTT_TX_DESC_FRM_ID_SET(local_word1, msdu_id);
 	*word1 = local_word1;