net/mlx4: fix handling of probing failure

net/mlx4: fix handling of probing failure

In mlx4 PCI probing, there are some validations for the Ethernet device
configuration.
From each PCI device the function creates one or two Ethernet devices.

When one of validations fails during the creation of the second device,
the first device is not freed what caused a memory leak.

Free it.

Fixes: 7fae69eeff13 ("mlx4: new poll mode driver")
Cc: stable@dpdk.org
Signed-off-by: Michael Baum <michaelba@nvidia.com>
Acked-by: Matan Azrad <matan@nvidia.com>
Tested-by: David Marchand <david.marchand@redhat.com>