media: atomisp: fix call to g_frame_interval

The media core has now a check if fi->pad is bigger than zero
or bigger than sd->entity.num_pads, if the media controller
is defined.

This causes a call to g_frame_interval to return -EINVAL.

Fix it by first cleaning up the struct.
Tested-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/staging/media/atomisp/pci/atomisp_cmd.c

@@ -109,7 +109,7 @@ struct atomisp_acc_pipe *atomisp_to_acc_pipe(struct video_device *dev)
 
 static unsigned short atomisp_get_sensor_fps(struct atomisp_sub_device *asd)
 {
-	struct v4l2_subdev_frame_interval fi;
+	struct v4l2_subdev_frame_interval fi = { 0 };
 	struct atomisp_device *isp = asd->isp;
 
 	unsigned short fps = 0;