libnvdimm, pfn: fix align attribute

commit af7d9f0c upstream.

Fix the format specifier so that the attribute can be parsed correctly.
Currently it returns decimal 1000 for a 4096-byte alignment.

Reported-by: Dave Jiang <dave.jiang@intel.com>
Fixes: 315c5625 ("libnvdimm, pfn: add 'align' attribute, default to HPAGE_SIZE")
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>