The caller of rtl8169_tso_csum_v2() frees the skb if false is returned.
eth_skb_pad() internally frees the skb on error what would result in a
double free. Therefore use __skb_put_padto() directly and instruct it
to not free the skb on error.

Fixes: b423e9ae ("r8169: fix offloaded tx checksum for small packets.")
Reported-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Link: https://lore.kernel.org/r/f7e68191-acff-9ded-4263-c016428a8762@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>