liquidio: fix use of pf in pass-through mode in a virtual machine

Fix problem when PF is used in pass-through mode in a VM (w/embedded f/w).

If host error reading PF num from CN23XX_PCIE_SRIOV_FDL reg,
try to retrieve PF num from SLI_PKT(0)_INPUT_CONTROL (initialized by f/w).

Signed-off-by: Rick Farrington <ricardo.farrington@cavium.com>
Signed-off-by: Felix Manlunas <felix.manlunas@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>