S2io: Fixes to enable multiple transmit fifo support

Fixes to enable multiple transmit fifos (upto a maximum of eight).
  - Moved single tx_lock from struct s2io_nic to struct fifo_info.
  - Moved single ufo_in_band_v structure from struct s2io_nic to struct
    fifo_info.
  - Assign the respective interrupt number for the transmitting fifo in the
    transmit descriptor (TXD).
- Added boundary checks for number of FIFOs enabled and FIFO length.

Signed-off-by: Surjit Reang <surjit.reang@neterion.com>
Signed-off-by: Sreenivasa Honnur <sreenivasa.honnur@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>