AP_RSSI: add PH2 ADC to ANA_PIN param values

libraries/AP_RSSI/AP_RSSI.cpp

@@ -41,7 +41,7 @@ const AP_Param::GroupInfo AP_RSSI::var_info[] = {
     // @Param: ANA_PIN
     // @DisplayName: Receiver RSSI analog sensing pin
     // @Description: This selects an analog pin where the receiver RSSI voltage will be read.
-    // @Values: 0:APM2 A0,1:APM2 A1,13:APM2 A13,11:Pixracer,13:Pixhawk ADC4,14:Pixhawk ADC3,15: Pixhawk ADC6,103:Pixhawk SBUS
+    // @Values: 0:APM2 A0,1:APM2 A1,13:APM2 A13,11:Pixracer,13:Pixhawk ADC4,14:Pixhawk ADC3,15:Pixhawk ADC6,103:Pixhawk SBUS,15:Pixhawk2 ADC
     // @User: Standard
     AP_GROUPINFO("ANA_PIN", 1, AP_RSSI, rssi_analog_pin,  BOARD_RSSI_ANA_PIN),