tools/testing/nvdimm: Add command debug messages

Arrange the for nfit_test_ctl() path to dump command payloads similarly
to the acpi_nfit_ctl() path. This is useful for comparing the
sequence of command events between an emulated ACPI-NFIT platform and a
real one.

Cc: Vishal Verma <vishal.l.verma@intel.com>
Cc: Dave Jiang <dave.jiang@intel.com>
Cc: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>