igc: enable XDP metadata in driver

Enabling the XDP bpf_prog access to data_meta area is a very small
change. Hint passing 'true' to xdp_prepare_buff().

The SKB layers can also access data_meta area, which required more
driver changes to support. Reviewers, notice the igc driver have two
different functions that can create SKBs, depending on driver config.

Hint for testers, ethtool priv-flags legacy-rx enables
the function igc_construct_skb()

 ethtool --set-priv-flags DEV legacy-rx on

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Tested-by: Nechama Kraus <nechamax.kraus@linux.intel.com>
Reviewed-by: Alexander Lobakin <alexandr.lobakin@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>