bnx2x: fix unload previous driver flow when flr-capable

The existing previous driver unload flow is flawed, causing the probe of
functions reaching the 'uncommon fork' in flr-capable devices to fail.

This patch resolves this, as well as fixing the flow for hypervisors which
disable flr capabilities from functions as they pass them as PDA to VMs,
as we cannot base the flow on the pci configuration space.

Signed-off-by: Yuval Mintz <yuvalmin@broadcom.com>
Signed-off-by: Ariel Elior <ariele@broadcom.com>
Signed-off-by: Eilon Greenstein <eilong@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>