net/packet: clear RX owner on VNET header error

Commit 61fad6816fc1 ("net/packet: tpacket_rcv: avoid a producer race
condition") added rx_owner_map and made tpacket_rcv() claim a V1 or V2
ring slot before converting the virtio-net header.  If the conversion
fails, the drop path leaves the slot claimed.

With a one-frame TPACKET_V2 ring, an unsupported UDP GSO packet leaves
the only slot unavailable, so the ring also drops the next valid packet.

Clear the ownership bit on this error path.  TPACKET_V3 already clears
its block state here.

Fixes: 61fad6816fc1 ("net/packet: tpacket_rcv: avoid a producer race condition")
Cc: stable@vger.kernel.org
Signed-off-by: Mark Amirkan <markdamirkan@gmail.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20260913-b4-send-packet-vnet-v1-1-5545ffb528ae@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>