net/mlx5: Release resource on error flow

Fix reference counting leakage when the event handler aborts due to an
unsupported event for the resource type.

Fixes: a14c2d4b

 ("net/mlx5_core: Warn on unsupported events of QP/RQ/SQ")
Signed-off-by: Moni Shoua <monis@mellanox.com>
Reviewed-by: Majd Dibbiny <majd@mellanox.com>
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>