net/mlx5: remove needless Tx queue initialization check

net/mlx5: remove needless Tx queue initialization check

The mlx5_txq_obj_new function defines a pointer named txq_data and
assign value into it. After assigning, the code writer is sure that the
variable does not point to NULL and even express it using assertion.

During the function, the function does dereferencing to the pointer
several times and at no point change its value. However, at the end of
the function at the error label when it wants to free one of the fields
of the structure that txq_data points to, it checks again whether
txq_data is invalid.
This check is unnecessary since it knows for sure that txq_data is
valid.

Remove the aforementioned needless check.

Fixes: 644906881881 ("net/mlx5: add free on completion queue")
Cc: stable@dpdk.org
Signed-off-by: Michael Baum <michaelba@mellanox.com>
Acked-by: Matan Azrad <matan@mellanox.com>