nvdimm core use nd_pfn_validate when looking for devdax or fsdax namespace. In this
case device resources are allocated against nd_namespace_io dev. In-order to
allow remap of range in nd_pfn_clear_memmap_error(), move the device memmap
area clearing while initializing pfn namespace. With this device
resource are allocated against nd_pfn and we can use nd_pfn->dev for remapping.

This also avoids calling nd_pfn_clear_mmap_errors twice. Once while probing the
namespace and second while initializing a pfn namespace.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Link: https://lore.kernel.org/r/20191101032728.113001-1-aneesh.kumar@linux.ibm.comSigned-off-by: Dan Williams <dan.j.williams@intel.com>