Add t-echo sx1268 support (#1657)

variants/t-echo/variant.h

@@ -124,6 +124,7 @@ External serial flash WP25R1635FZUIL0
  */
 
 #define USE_SX1262
+#define USE_SX1268
 #define SX126X_CS (0 + 24) // FIXME - we really should define LORA_CS instead
 #define SX126X_DIO1 (0 + 20)
 // Note DIO2 is attached internally to the module to an analog switch for TX/RX switching