Update: Removed duplicate power down function

Add: gnss power mode function

components/esp_modem/src/esp_modem_modules.cpp

@@ -55,16 +55,16 @@ command_result SIM7600::get_battery_status(int &voltage, int &bcs, int &bcl)
     return dce_commands::get_battery_status_sim7xxx(dte.get(), voltage, bcs, bcl);
 }
 
-command_result SIM7600::power_down()
-{
-    return dce_commands::power_down_sim76xx(dte.get());
-}
-
 command_result SIM7600::set_network_bands(const std::string& mode, const int* bands, int size)
 {
     return dce_commands::set_network_bands_sim76xx(dte.get(), mode, bands, size);
 }
 
+command_result SIM7600::set_gnss_power_mode(int mode)
+{
+    return dce_commands::set_gnss_power_mode_sim76xx(dte.get(), mode);
+}
+
 command_result SIM7600::power_down()
 {
     return dce_commands::power_down_sim76xx(dte.get());