ui/device: fix uninitialized variable awake (#22983)

selfdrive/ui/ui.h

@@ -188,7 +188,7 @@ private:
   // auto brightness
   const float accel_samples = 5*UI_FREQ;
 
-  bool awake;
+  bool awake = false;
   int awake_timeout = 0;
   float accel_prev = 0;
   float gyro_prev = 0;