nfit: fix translation of command status results

When transportation of the command completes successfully, it indicates
that the 'status' result is valid.  Fix the missed checking and
translation of the status field at the end of acpi_nfit_ctl().
Otherwise, we fail to handle reported errors and assume commands
complete successfully.

Reported-by: Linda Knippers <linda.knippers@hpe.com>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>