(probably) fix screen power and lora amp power on tlora v1

Supposedly this board is deprecated/busted according to reddit.
While doing other cleanup I noticed possibly why - the VEXT_ENABLE
was having no effect because it didn't specify HIGH or LOW for that signal

I don't have this board easily accessible, but given that the comment says
this signal is active low and supposedly the board doesn't work anyways
this might be why.

variants/tlora_v1/variant.h

@@ -4,8 +4,9 @@
 #define RESET_OLED 16 // If defined, this pin will be used to reset the display controller
 
 #define VEXT_ENABLE 21 // active low, powers the oled display and the lora antenna boost
-#define LED_PIN 2      // If defined we will blink this LED
-#define BUTTON_PIN 0   // If defined, this will be used for user button presses
+#define VEXT_ON_VALUE LOW
+#define LED_PIN 2    // If defined we will blink this LED
+#define BUTTON_PIN 0 // If defined, this will be used for user button presses
 #define BUTTON_NEED_PULLUP
 #define EXT_NOTIFY_OUT 13 // Default pin to use for Ext Notify Module.