S2io: Removed receive buffer replenishment tasklet

- Removed receive buffer replenishment tasklet s2io_tasklet and instead
  allocating the receive buffers in either the interrupt handler (no napi)
  or the napi handler (napi enabled).

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 <jgarzik@redhat.com>