[ppc440SPe] Graceful recovery from machine check during PCIe configuration

[ppc440SPe] Graceful recovery from machine check during PCIe configuration

During config transactions on the PCIe bus an attempt to scan for a
non-existent device can lead to a machine check exception with certain
peripheral devices. In order to avoid crashing in such scenarios the
instrumented versions of the config cycle read routines are introduced, so
the exceptions fixups framework can gracefully recover.

Signed-off-by: Grzegorz Bernacki <gjb@semihalf.com>
Acked-by: Rafal Jaworowski <raj@semihalf.com>