tools/testing/nvdimm: Fix fallthrough warning

tools/testing/nvdimm: Fix fallthrough warning

Use the expected 'fall through' designation to fix:

    tools/testing/nvdimm/test/nfit.c: In function ‘nd_intel_test_finish_query’:
    tools/testing/nvdimm/test/nfit.c:433:13: warning: this statement may fall through [-Wimplicit-fallthrough=]
       fw->state = FW_STATE_UPDATED;
       ~~~~~~~~~~^~~~~~~~~~~~~~~~~~
    tools/testing/nvdimm/test/nfit.c:435:2: note: here
      case FW_STATE_UPDATED:
      ^~~~

Reviewed-by: Vishal Verma <vishal.l.verma@intel.com>
Link: https://lore.kernel.org/r/156521347159.1442374.1381360879102718899.stgit@dwillia2-desk3.amr.corp.intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>