net/mlx5: Fix length of irq_index in chars

The maximum irq_index can be 2047, This means irq_name should have 4
characters reserve for the irq_index. Hence, increase it to 4.

Fixes: 3af26495

 ("net/mlx5: Enlarge interrupt field in CREATE_EQ")
Signed-off-by: Shay Drory <shayd@nvidia.com>
Reviewed-by: Parav Pandit <parav@nvidia.com>
Signed-off-by: Saeed Mahameed <saeedm@nvidia.com>