net: enetc: keep track of correct Tx BD count in enetc_map_tx_tso_buffs()

net: enetc: keep track of correct Tx BD count in enetc_map_tx_tso_buffs()

When creating a TSO header, if the skb is VLAN tagged, the extended BD
will be used and the 'count' should be increased by 2 instead of 1.
Otherwise, when an error occurs, less tx_swbd will be freed than the
actual number.

Fixes: fb8629e2cbfc ("net: enetc: add support for software TSO")
Cc: stable@vger.kernel.org
Suggested-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: Wei Fang <wei.fang@nxp.com>
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Claudiu Manoil <claudiu.manoil@nxp.com>
Link: https://patch.msgid.link/20250224111251.1061098-3-wei.fang@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>