ena: Disable meta descriptor caching for netmap

If LLQ is being used, ena_tx_ctx.meta_valid must stay enabled. This
fixes netmap support on latest generation ENA HW and aligns it with the
core driver behavior.

As netmap doesn't support any csum offloads, the
adapter->disable_meta_caching value can be simply passed to the HW.

Obtained from: Semihalf
MFC after: 2 weeks
Sponsored by: Amazon, Inc.