r8169: don't increment tx_dropped in case of NETDEV_TX_BUSY

r8169: don't increment tx_dropped in case of NETDEV_TX_BUSY

The skb isn't consumed in case of NETDEV_TX_BUSY, therefore don't
increment the tx_dropped counter.

Fixes: 188f4af04618 ("r8169: use NETDEV_TX_{BUSY/OK}")
Cc: stable@vger.kernel.org
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Wojciech Drewek <wojciech.drewek@intel.com>
Link: https://patch.msgid.link/bbba9c48-8bac-4932-9aa1-d2ed63bc9433@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>