net/ena: support large LLQ headers

net/ena: support large LLQ headers

Default LLQ (Low-latency queue) maximum header size is 96 bytes and can
be too small for some types of packets - like IPv6 packets with multiple
extension. This can be fixed, by using large LLQ headers.

If the device supports larger LLQ headers, the user can activate them by
using device argument 'large_llq_hdr' with value '1'.

If the device isn't supporting this feature, the default value (96B)
will be used.

Signed-off-by: Michal Krawczyk <mk@semihalf.com>
Reviewed-by: Igor Chauskin <igorch@amazon.com>
Reviewed-by: Guy Tzalik <gtzalik@amazon.com>