avoid unused-variable warning

Avoid warning when compiled with All warnings enabled.
.../src/NimBLEScan.cpp: In member function 'void NimBLEScanResults::dump() const':
.../src/NimBLEScan.cpp:481:22: warning: unused variable 'dev' [-Wunused-variable]
  481 |     for (const auto& dev : m_deviceVec) {
      |                      ^~~

Author: mazgch

src/NimBLEScan.cpp

@@ -478,9 +478,11 @@ void NimBLEScan::clearResults() {
  * @brief Dump the scan results to the log.
  */
 void NimBLEScanResults::dump() const {
+#if CONFIG_NIMBLE_CPP_LOG_LEVEL >=3
     for (const auto& dev : m_deviceVec) {
         NIMBLE_LOGI(LOG_TAG, "- %s", dev->toString().c_str());
     }
+#endif
 } // dump
 
 /**