AP_Arming: warn about uncalibrated throttle but do not fail check

We can tighten this check up later, and will allow us to use
this common function for Plane and Rover in the future

libraries/AP_Arming/AP_Arming.cpp

@@ -600,21 +600,26 @@ bool AP_Arming::rc_checks_copter_sub(const bool display_failure, const RC_Channe
             }
             ret = false;
         }
+        bool fail = true;
         if (i == 2) {
             // skip checking trim for throttle as older code did not check it
-            continue;
+            fail = false;
         }
         if (channel->get_radio_trim() < channel->get_radio_min()) {
             if (display_failure) {
                 gcs().send_text(MAV_SEVERITY_CRITICAL,"PreArm: %s radio trim below min", channel_name);
             }
-            ret = false;
+            if (fail) {
+                ret = false;
+            }
         }
         if (channel->get_radio_trim() > channel->get_radio_max()) {
             if (display_failure) {
                 gcs().send_text(MAV_SEVERITY_CRITICAL,"PreArm: %s radio trim above max", channel_name);
             }
-            ret = false;
+            if (fail) {
+                ret = false;
+            }
         }
     }
     return ret;