net/mlx5e: Do not reduce LRO WQE size when not using build_skb

When rq_type is Striding RQ, no room of SKB_RESERVE is needed
as SKB allocation is not done via build_skb.

Fixes: e4b85508 ("net/mlx5e: Slightly reduce hardware LRO size")
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>