More RAK6421 work (#9813)

* Add Portduino Enable pins

* Add hat plus custom fields

* Punt on the GPIO device detection for now

* Simplify TX_GAIN_LORA for RAK13302

---------

Co-authored-by: Ben Meadors <benmmeadors@gmail.com>

src/platform/portduino/PortduinoGlue.h

@@ -52,6 +52,7 @@ struct pinMapping {
     int gpiochip;
     int line;
     bool enabled = false;
+    bool default_high = false;
 };
 
 extern std::ofstream traceFile;
@@ -195,6 +196,8 @@ extern struct portduino_config_struct {
     int maxtophone = 100;
     int MaxNodes = 200;
 
+    std::unordered_map<std::string, std::string> hat_plus_custom_fields;
+
     pinMapping *all_pins[21] = {&lora_cs_pin,
                                 &lora_irq_pin,
                                 &lora_busy_pin,