net/mlx4: Remove shared_ports variable at mlx4_enable_msi_x

If we get MAX_MSIX interrupts would like to have each receive ring
with his own msix interrupt line. Do not need the shared_ports
variable at mlx4_enable_msix

Fixes: 9293267a

 ('net/mlx4_core: Capping number of requested MSIXs to MAX_MSIX')
Signed-off-by: Carol L Soto <clsoto@linux.vnet.ibm.com>
Acked-by: Matan Barak <matanb@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>