Add reset to joystick mixer

include/joystick_mixer.h

@@ -22,9 +22,9 @@ class JoystickMixer
     JoystickMixer(int32_t usb_x, int32_t usb_y, int32_t usb_r);
 
     void init(int32_t usb_x, int32_t usb_y, int32_t usb_r);
+    void reset();
 
     void mix(float x, float y);
-
     void mix_delta(float dx, float dy);
 
     void getXY(int32_t &x, int32_t &y);

src/joystick_mixer.cpp

@@ -13,6 +13,11 @@ void JoystickMixer::init(int32_t usb_x, int32_t usb_y, int32_t usb_r)
     this->usb_y = usb_y;
     this->usb_r = usb_r;
 
+    reset();
+}
+
+void JoystickMixer::reset()
+{
     this->x = 0;
     this->y = 0;
     this->dx = 0;