Some instances of pci_ops initialization rely on the read/write members'
location in the struct.  This is fragile and may break when adding new
members to the beginning of the struct.

No functional change.
Signed-off-by: Rob Herring <robh@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: David Howells <dhowells@redhat.com>