net: mvneta: Add metadata support for xdp mode

net: mvneta: Add metadata support for xdp mode

Set metadata size building the skb from xdp_buff in mvneta driver
mvneta sets xdp headroom to:

MVNETA_MH_SIZE + MVNETA_SKB_HEADROOM

where

MVNETA_MH_SIZE 2
MVNETA_SKB_HEADROOM max(NET_SKB_PAD, XDP_PACKET_HEADROOM)

so the headroom is large enough to contain xdp_frame and xdp metadata.

Reviewed-by: Michal Kubiak <michal.kubiak@intel.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://patch.msgid.link/20250318-mvneta-xdp-meta-v2-1-b6075778f61f@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>