dax/pmem: Fix whitespace in dax_pmem

A few lines were whitespace damaged, with spaces at the start instead of
tabs. This was noticed while debugging an nfit_test failure, so fix
them.

Cc: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>