S2io: Added napi support when MSIX is enabled.

- Added napi support when MSIX is enabled.
- Moved test_msi function from s2io_open to probe function.

Signed-off-by: Sreenivasa Honnur <sreenivasa.honnur@neterion.com>
Signed-off-by: Ramkrishna Vepa <ram.vepa@neterion.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>