[nrf noup] wifi: Fix 5GHz association

Wi-Fi stack recently introduced a check for valid band value and the
default value of 0 (memset) means only 2.4GHz, so, 5GHz Wi-Fi
associations will fail.

Fix the default to Unknown to scan all supported bands.

Fixes KRKNWK-18035.

Signed-off-by: Chaitanya Tata <[email protected]>
(cherry picked from commit e8e30f9)

src/platform/nrfconnect/wifi/WiFiManager.cpp

@@ -363,6 +363,7 @@ void WiFiManager::ScanResultHandler(Platform::UniquePtr<uint8_t> data)
             Instance().mWiFiParams.mParams.timeout = Instance().mHandling.mConnectionTimeout.count();
             Instance().mWiFiParams.mParams.channel = WIFI_CHANNEL_ANY;
             Instance().mWiFiParams.mRssi           = scanResult->rssi;
+            Instance().mWiFiParams.mParams.band    = WIFI_FREQ_BAND_UNKNOWN;
             Instance().mSsidFound                  = true;
         }
     }