S2io: Fixes to enable multiple transmit fifos

Multiple transmit fifo initialization -
  - Assigned equal scheduling priority for all configured FIFO's.
  - Modularized transmit traffic interrupt initialization since it is executed in
    s2io_card_up and s2io_link. Enable continuous tx interrupt when link is UP
    and vice verse.
  - Enable transmit interrupts for all configured transmit fifos.
  - Fixed typo errors.

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>