PCI/portdrv: Remove unused resume err_handler

PCI/portdrv: Remove unused resume err_handler

Commit 3e41a317ae45 ("PCI/AER: Remove unused aer_error_resume()")
removed the resume err_handler from AER.  Since no other port service
implements the callback, support for it can be removed from portdrv.
It can be revived later if need be, preferably by re-using the
pcie_port_device_iter() iterator.

Link: https://lore.kernel.org/r/25334149b604e005058aeb0fdf51e01f991d5d74.1627638184.git.lukas@wunner.de
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Keith Busch <kbusch@kernel.org>