vtol defaults: use parameters for pwm values

ROMFS/px4fmu_common/init.d/13001_caipirinha_vtol

@@ -38,8 +38,6 @@ fi
 set MIXER caipirinha_vtol
 
 set PWM_OUT 1234
-set PWM_RATE 400
-set PWM_MAX 2000
 param set VT_MOT_COUNT 2
 param set VT_IDLE_PWM_MC  1080
 param set VT_TYPE 0

ROMFS/px4fmu_common/init.d/rc.vtol_defaults

@@ -26,6 +26,9 @@ then
 	param set MPC_ACC_HOR_MAX 2.0
 fi
 
-set PWM_DISARMED 900
-set PWM_MIN 1000
-set PWM_MAX 2000
+# set environment variables (!= parameters)
+set PWM_RATE 400
+# tell the mixer to use parameters for these instead
+set PWM_DISARMED p:PWM_DISARMED
+set PWM_MIN p:PWM_MIN
+set PWM_MAX p:PWM_MAX