REO/Grande defect AR2305 can cause TLB fetch timeouts if entries
  are purged while in use.  Round up IOVA allocations to power-of-two
  boundaries to prevent this.  This is originally due to Alex Williamson.
Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>