net: airoha: Move DSA tag in DMA descriptor

Packet Processor Engine (PPE) module reads DSA tags from the DMA descriptor
and requires untagged DSA packets to properly parse them. Move DSA tag
in the DMA descriptor on TX side and read DSA tag from DMA descriptor
on RX side. In order to avoid skb reallocation, store tag in skb_dst on
RX side.
This is a preliminary patch to enable netfilter flowtable hw offloading
on EN7581 SoC.

Tested-by: Sayantan Nandy <sayantan.nandy@airoha.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>