libnvdimm/namespace: Fix visibility of namespace resource attribute

libnvdimm/namespace: Fix visibility of namespace resource attribute

Legacy pmem namespaces lost support for the "resource" attribute when
the code was cleaned up to put the permission visibility in the
declaration. Restore this by listing 'resource' in the default
attributes.

A new ndctl regression test for pfn_to_online_page() corner cases builds
on this fix.

Fixes: bfd2e9140656 ("libnvdimm: Simplify root read-only definition for the 'resource' attribute")
Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/161052334995.1805594.12054873528154362921.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>