AP_BattMonitor: param desc explicitly list Pixhawk 2 PM1 pins

There is confusion over which pins to use with the pixhawk 2, updated documentation to explicitly state the PM1 pins as being the same as the original pixhawk

libraries/AP_BattMonitor/AP_BattMonitor.cpp

@@ -17,14 +17,14 @@ const AP_Param::GroupInfo AP_BattMonitor::var_info[] = {
     // @Param: _VOLT_PIN
     // @DisplayName: Battery Voltage sensing pin
     // @Description: Setting this to 0 ~ 13 will enable battery voltage sensing on pins A0 ~ A13. On the PX4-v1 it should be set to 100. On the Pixhawk, Pixracer and NAVIO boards it should be set to 2, Pixhawk2 Power2 is 13.
-    // @Values: -1:Disabled, 0:A0, 1:A1, 2:Pixhawk/Pixracer/Navio2, 13:Pixhawk2_PM2, 100:PX4-v1
+    // @Values: -1:Disabled, 0:A0, 1:A1, 2:Pixhawk/Pixracer/Navio2/Pixhawk2_PM1, 13:Pixhawk2_PM2, 100:PX4-v1
     // @User: Standard
     AP_GROUPINFO("_VOLT_PIN", 1, AP_BattMonitor, _volt_pin[0], AP_BATT_VOLT_PIN),
 
     // @Param: _CURR_PIN
     // @DisplayName: Battery Current sensing pin
     // @Description: Setting this to 0 ~ 13 will enable battery current sensing on pins A0 ~ A13. On the PX4-v1 it should be set to 101. On the Pixhawk, Pixracer and NAVIO boards it should be set to 3, Pixhawk2 Power2 is 14.
-    // @Values: -1:Disabled, 1:A1, 2:A2, 3:Pixhawk/Pixracer/Navio2, 14:Pixhawk2_PM2, 101:PX4-v1
+    // @Values: -1:Disabled, 1:A1, 2:A2, 3:Pixhawk/Pixracer/Navio2/Pixhawk2_PM1, 14:Pixhawk2_PM2, 101:PX4-v1
     // @User: Standard
     AP_GROUPINFO("_CURR_PIN", 2, AP_BattMonitor, _curr_pin[0], AP_BATT_CURR_PIN),