net/mlx5e: Generalize tx helper functions for different SQ types

In the next patches we will introduce different SQ types, for that we here
generalize some TX helper functions to work with more basic SQ parameters,
in order to re-use them for the different SQ types.

Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Reviewed-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>