libnvdimm, pfn: 'resource'-address and 'size' attributes for pfn devices

Currenty with a raw mode pmem namespace the physical memory address range for
the device can be obtained via /sys/block/pmemX/device/{resource|size}.  Add
similar attributes for pfn instances that takes the struct page memmap and
section padding into account.

Reported-by: Haozhong Zhang <haozhong.zhang@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>