bnxt_en: fix pci cleanup in bnxt_init_one() failure path

In the bnxt_init_one() failure path, bar1 and bar2 are not
being unmapped.  This commit fixes this issue.  Reorganize the
code so that bnxt_init_one()'s failure path and bnxt_remove_one()
can call the same function to do the PCI cleanup.

Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>