Use KCT8270N gain

Author: CapnBry

TX/Radiomaster AX12.json

@@ -23,7 +23,7 @@
  "power_values": [-18, -15, -12, -9, -5],
  "power_values_dual": [-18, -15, -13, -9, -5],
  "radio_rfsw_ctrl": [15, 0, 4, 12, 12, 2, 0, 1],
- "power_lna_gain": 15,
+ "power_lna_gain": 14,
 
  "led_rgb": 22,
  "led_rgb_isgrb": true,