PCI: Uninline PCI bus accessors for better ftracing

The PCI bus config accessors could be inlined into other accessor
functions, which makes it so they can't be traced.  Force them to never be
inlined so that ftrace can hook into these functions.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>