net/mlx5e: RX, Remove HW LRO support in legacy RQ

Current LRO implementation in Legacy RQ uses high-order pages.
In downstream patches of this series we complete the transition
to using only order-0 pages in RX datapath (which was already done
in Striding RQ).

Unlike the more advanced Striding RQ, Legacy RQ does not make reuse
of any non-consumed buffers of non-full LRO sessions, and combining
it with order-0 pages has many performance drawbacks.

Hence, here we totally remove LRO support in Legacy RQ.
This guarantees having no out-of-order completions, which allows using
a cyclic work queue (instead of a linked-list) in a downstream patch.

Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>