powerpc/eeh: EEH support for VFIO PCI device

The patch exports functions to be used by new VFIO ioctl command,
which will be introduced in subsequent patch, to support EEH
functinality for VFIO PCI devices.

Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Acked-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>