bnxt_en: Re-write PCI BARs after PCI fatal error.

When a PCIe fatal error occurs, the internal latched BAR addresses
in the chip get reset even though the BAR register values in config
space are retained.

pci_restore_state() will not rewrite the BAR addresses if the
BAR address values are valid, causing the chip's internal BAR addresses
to stay invalid.  So we need to zero the BAR registers during PCIe fatal
error to force pci_restore_state() to restore the BAR addresses.  These
write cycles to the BAR registers will cause the proper BAR addresses to
latch internally.

Fixes: 6316ea6d

 ("bnxt_en: Enable AER support.")
Signed-off-by: Vasundhara Volam <vasundhara-v.volam@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>