[PATCH v2] net: stmmac: Modify the judgment condition of "tx_avail" from 1 to 2

[Jakub Kicinski]

On Tue,  2 Dec 2025 15:43:59 +0800 2694439648 at qq.com wrote:
> -	if (unlikely(stmmac_tx_avail(priv, queue) <= (MAX_SKB_FRAGS + 1))) {
> +	if (unlikely(stmmac_tx_avail(priv, queue) <= (MAX_SKB_FRAGS + 2))) {

Also, if there isn't a comment already somewhere - it's worth
documenting what the + 2 stands for. head buffer + vlan + frags ?