Revert duplicate "PCI: pciehp: Prevent NULL dereference during probe"

This reverts bceee4a9 ("PCI: pciehp: Prevent NULL dereference during
probe") because it was accidentally applied twice:

  62e4492c ("PCI: Prevent NULL dereference during pciehp probe")
  bceee4a9 ("PCI: pciehp: Prevent NULL dereference during probe")

Revert the latter to dispose of the duplicated code block.

[bhelgaas: tidy changelog, drop stable tag]
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: Andreas Noever <andreas.noever@gmail.com>