net: renesas: rswitch: fix leaked pointer on error path

If error path is taken while filling descriptor for a frame, skb
pointer is left in the entry. Later, on the ring entry reuse, the
same entry could be used as a part of a multi-descriptor frame,
and skb for that new frame could be stored in a different entry.

Then, the stale pointer will reach the completion routine, and passed
to the release operation.

Fix that by clearing the saved skb pointer at the error path.

Fixes: d2c96b9d ("net: rswitch: Add jumbo frames handling for TX")
Signed-off-by: Nikita Yushchenko <nikita.yoush@cogentembedded.com>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Link: https://patch.msgid.link/20241208095004.69468-4-nikita.yoush@cogentembedded.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>