Notify scan-only mode to driver for power saving

If Wi-Fi driver knows it's in scan-only mode, it can save more power
than connect mode.

This change adds setScanMode in IWifiStaIface to allow Wi-Fi framework
to notify scan-only mode change to Wi-Fi driver.

Bug: 177811719
Test: atest VtsHalWifiV1_5TargetTest

Change-Id: I1dfbc24a0a3272c1341223aff36656be4a6fd21b
diff --git a/wifi/1.5/default/wifi_sta_iface.h b/wifi/1.5/default/wifi_sta_iface.h
index 94873c9..f9058b8 100644
--- a/wifi/1.5/default/wifi_sta_iface.h
+++ b/wifi/1.5/default/wifi_sta_iface.h
@@ -114,6 +114,8 @@
                                setMacAddress_cb hidl_status_cb) override;
     Return<void> getFactoryMacAddress(
         getFactoryMacAddress_cb hidl_status_cb) override;
+    Return<void> setScanMode(bool enable,
+                             setScanMode_cb hidl_status_cb) override;
 
    private:
     // Corresponding worker functions for the HIDL methods.
@@ -164,6 +166,7 @@
     WifiStatus setMacAddressInternal(const std::array<uint8_t, 6>& mac);
     std::pair<WifiStatus, std::array<uint8_t, 6>>
     getFactoryMacAddressInternal();
+    WifiStatus setScanModeInternal(bool enable);
 
     std::string ifname_;
     std::weak_ptr<legacy_hal::WifiLegacyHal> legacy_hal_;