s2io: Removed enabling of some of the unused interrupts.

Removed unused code in en_dis_able_nic_intrs(), TX_DMA_INTR, RX_DMA_INTR,
TX_XGXS_INTR, MC_INTR

Signed-off-by: Sivakumar Subramani <sivakumar.subramani@neterion.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>