Fix issues introduced in 57b6135e54

- std=c++.. is not required because CMAKE_CXX_STANDARD is set
- nullptr check breaks the test because we rely on nullptr as an api for
  checking feature availability.
- enum number setting is unnecessary

Change-Id: I393e6dd3f292b7fa4198302f140c0443ba5e50f5
Signed-off-by: Galantsev, Dmitrii <dmitrii.galantsev@amd.com>

src/rocm_smi.cc

@@ -2776,9 +2776,6 @@ rsmi_dev_od_volt_info_get(uint32_t dv_ind, rsmi_od_volt_freq_data_t *odv) {
   ss << __PRETTY_FUNCTION__ << "| ======= start =======";
   LOG_TRACE(ss);
   DEVICE_MUTEX
-  if (odv == nullptr) {
-    return RSMI_STATUS_INVALID_ARGS;
-  }
   CHK_SUPPORT_NAME_ONLY(odv)
   rsmi_status_t ret = get_od_clk_volt_info(dv_ind, odv);