APM: fixed default flap speed

the default of 255 translates to -1 as a AP_Int8, so use zero to mean
no flaps

ArduPlane/Attitude.pde

@@ -398,9 +398,9 @@ static void set_servos(void)
 			} else {
 				flapSpeedSource = g.throttle_cruise;
 			}
-			if ( flapSpeedSource > g.flap_1_speed) {
+			if ( g.flap_1_speed != 0 && flapSpeedSource > g.flap_1_speed) {
 				g_rc_function[RC_Channel_aux::k_flap_auto]->servo_out = 0;
-			} else if (flapSpeedSource > g.flap_2_speed) {
+			} else if (g.flap_2_speed != 0 && flapSpeedSource > g.flap_2_speed) {
 				g_rc_function[RC_Channel_aux::k_flap_auto]->servo_out = g.flap_1_percent;
 			} else {
 				g_rc_function[RC_Channel_aux::k_flap_auto]->servo_out = g.flap_2_percent;

ArduPlane/config.h

@@ -317,13 +317,13 @@
 # define FLAP_1_PERCENT 0
 #endif
 #ifndef FLAP_1_SPEED
-# define FLAP_1_SPEED 255
+# define FLAP_1_SPEED 0
 #endif
 #ifndef FLAP_2_PERCENT
 # define FLAP_2_PERCENT 0
 #endif
 #ifndef FLAP_2_SPEED
-# define FLAP_2_SPEED 255
+# define FLAP_2_SPEED 0
 #endif
 //////////////////////////////////////////////////////////////////////////////
 // FLIGHT_MODE