drivers/video/isx019: Fix the default_value of some parameters

Because the exposure time and ISO sensitivity are adjusted automatically
by default, the default value can not be defined.
So, return the value out of range as the default_value of
ioctl(VIDIOC_QUERYCTRL).

drivers/video/isx019.c

@@ -1975,7 +1975,7 @@ static int isx019_get_supported_value(FAR struct imgsensor_s *sensor,
       case IMGSENSOR_ID_EXPOSURE_ABSOLUTE:
         val->type = IMGSENSOR_CTRL_TYPE_INTEGER;
         SET_RANGE(val->u.range, MIN_EXPOSURETIME, MAX_EXPOSURETIME,
-                                STEP_EXPOSURETIME, def->exptime);
+                                STEP_EXPOSURETIME, 0); /* 0 means undefined */
         break;
 
       case IMGSENSOR_ID_AUTO_N_PRESET_WB:
@@ -1997,7 +1997,7 @@ static int isx019_get_supported_value(FAR struct imgsensor_s *sensor,
         SET_DISCRETE(val->u.discrete,
                      NR_ISO,
                      g_isx019_iso,
-                     def->iso);
+                     0); /* 0 means undefined */
         break;
 
       case IMGSENSOR_ID_ISO_SENSITIVITY_AUTO: