Remove SYS_USE_IO param

The param is not really required anymore with the actuator
configuration. Also, when it is set to 0, RC doesn't work for some
boards which would be nice to avoid.

Signed-off-by: Julian Oes <julian@oes.ch>

boards/holybro/durandal-v1/init/rc.board_defaults

@@ -11,5 +11,3 @@ param set-default BAT2_A_PER_V 36.367515152
 
 # Enable IMU thermal control
 param set-default SENS_EN_THERMAL 1
-
-param set-default SYS_USE_IO 1

boards/holybro/pix32v5/init/rc.board_defaults

@@ -9,7 +9,5 @@ param set-default BAT2_V_DIV 18.1
 param set-default BAT1_A_PER_V 36.367515152
 param set-default BAT2_A_PER_V 36.367515152
 
-param set-default SYS_USE_IO 1
-
 rgbled_pwm start
 safety_button start