nvdimm: fix PHYS_PFN/PFN_PHYS mixup

nd_activate_region() iomaps any hint addresses required when activating
a region. To prevent duplicate mappings it checks the PFN of the hint to
be mapped against the PFNs of the already mapped hints. Unfortunately it
doesn't convert the PFN back into a physical address before passing it
to devm_nvdimm_ioremap(). Instead it applies PHYS_PFN a second time
which ends about as well as you would imagine.
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

drivers/nvdimm/region_devs.c

@@ -57,7 +57,7 @@ static int nvdimm_map_flush(struct device *dev, struct nvdimm *nvdimm, int dimm,
 					ndrd->flush_wpq[dimm][j] & PAGE_MASK);
 		else
 			flush_page = devm_nvdimm_ioremap(dev,
-					PHYS_PFN(pfn), PAGE_SIZE);
+					PFN_PHYS(pfn), PAGE_SIZE);
 		if (!flush_page)
 			return -ENXIO;
 		ndrd->flush_wpq[dimm][i] = flush_page