net/mlx5e: Remove unnecessary checks when setting num channels

Boundaries checks for the number of RX and TX should be checked by the
caller and not in the driver.

Signed-off-by: Eran Ben Elisha <eranbe@mellanox.com>
Signed-off-by: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>