net/mlx5e: Use u8 instead of int for LRO number of segments

Range of LRO number of segments fits in u8.
Also, bring initialization and declaration together to
save code.

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