net/mlx5e: Fix use-after-free after xdp_return_frame

xdp_return_frame releases the frame. It leads to releasing the page, so
it's not allowed to access xdpi.xdpf->len after that, because xdpi.xdpf
is at xdp->data_hard_start after convert_to_xdp_frame. This patch moves
the memory access to precede the return of the frame.

Fixes: 58b99ee3 ("net/mlx5e: Add support for XDP_REDIRECT in device-out side")
Signed-off-by: Maxim Mikityanskiy <maximmi@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>