Revert "ozwpan: replace kfree_skb with dev_kfree_skb in ozproto.c"

This reverts commit 5109c8a0.

I shouldn't have applied this, my fault...

Cc: Xenia Ragiadakou <burzalodowa@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>