PCI: altera: Extract TLP completion status correctly

Previously we extracted 'Completion Status' from b14:12, but it is actually
b15:13.  Extract it from the correct bits.

Signed-off-by: Hu <Yadi&lt;yadi.hu@windriver.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Ley Foon Tan <ley.foon.tan@intel.com>