Add API "startSubsystemRestart" and callback function

In order to trigger subsystem restart to reload wlan firmware,
this change adds an API for framework and vendor HAL.
Meanwhile, create new callback function for subsystem restart instead of
 general callback "onFailure()".

Bug: 178126071
Test: vendor HAL can received API call
      subsystem restart will callback "onSubsystemRestart()"

Change-Id: If3dc84049a9171677ad281c9bcc67a44dc722bdb
diff --git a/wifi/1.5/default/wifi_legacy_hal.h b/wifi/1.5/default/wifi_legacy_hal.h
index 8ebc66a..2bb7631 100644
--- a/wifi/1.5/default/wifi_legacy_hal.h
+++ b/wifi/1.5/default/wifi_legacy_hal.h
@@ -716,6 +716,8 @@
     std::pair<wifi_error, std::vector<wifi_usable_channel>> getUsableChannels(
         uint32_t band_mask, uint32_t iface_mode_mask, uint32_t filter_mask);
 
+    wifi_error triggerSubsystemRestart();
+
    private:
     // Retrieve interface handles for all the available interfaces.
     wifi_error retrieveIfaceHandles();