feat: rename ARM_CHN to RC_ARM_CHN for consistency (#484)

BREAKING CHANGE: rename ARM_CHN parameter

Author: JMoore5353

src/param.cpp

@@ -461,7 +461,7 @@ void Params::set_defaults(void)
   init_param_int(PARAM_RC_ATTITUDE_OVERRIDE_CHANNEL, "RC_ATT_OVRD_CHN", 4); // RC switch mapped to attitude override [0 indexed, -1 to disable] | 4 | 7
   init_param_int(PARAM_RC_THROTTLE_OVERRIDE_CHANNEL, "RC_THR_OVRD_CHN", 4); // RC switch channel mapped to throttle override [0 indexed, -1 to disable] | 4 | 7
   init_param_int(PARAM_RC_ATT_CONTROL_TYPE_CHANNEL,  "RC_ATT_CTRL_CHN",-1); // RC switch channel mapped to attitude control type [0 indexed, -1 to disable] | 4 | 7
-  init_param_int(PARAM_RC_ARM_CHANNEL, "ARM_CHN",-1); // RC switch channel mapped to arming (only if PARAM_ARM_STICKS is false) [0 indexed, -1 to disable] | 4 | 7
+  init_param_int(PARAM_RC_ARM_CHANNEL, "RC_ARM_CHN",-1); // RC switch channel mapped to arming (only if PARAM_ARM_STICKS is false) [0 indexed, -1 to disable] | 4 | 7
   init_param_int(PARAM_RC_NUM_CHANNELS, "RC_NUM_CHN", 6); // number of RC input channels | 1 | 8
 
   init_param_int(PARAM_RC_SWITCH_5_DIRECTION, "SWITCH_5_DIR", 1); // RC switch 5 toggle direction | -1 | 1