S2io: Move all the transmit completions to a single msi-x (alarm) vector

- Move all the transmit completions to a single msi-x (alarm) vector.
- Enable the continuous timer interrupt for only one transmit fifo.

Signed-off-by: Santosh Rastapur <santosh.rastapur@neterion.com>
Signed-off-by: Ramkrishna Vepa <ram.vepa@neterion.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>