bnx2x: Allow recovery from second slot reset

As part of PCIe Advanced Error Reporting flow, if a fatal PCI error occurs,
the AER driver will cause bnx2x's PCI-core to reset. The driver's PCI error
handlers will in turn restore the PCI configuration space values by calling
`pci_restore_state'.

However, as bnx2x does not save the PCI configuration after restoration,
An additional fatal PCI error will leave the function in an unstable state
until reboot, as the registers in the PCI configuration space will contain
reset values.

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>