[S2IO]: Making MSIX as default intr_type

- Making MSIX as default intr_type
- Driver will test MSI-X by issuing test MSI-X vector and if fails it will
  fallback to INTA

Signed-off-by: Sivakumar Subramani <sivakumar.subramani@neterion.com>
Signed-off-by: Ramkrishna Vepa <ram.vepa@neterion.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
Signed-off-by: David S. Miller <davem@davemloft.net>