media: mc-device.c: don't memset __user pointer contents

You can't memset the contents of a __user pointer. Instead, call copy_to_user to
copy links.reserved (which is zeroed) to the user memory.

This fixes this sparse warning:

SPARSE:drivers/media/mc/mc-device.c drivers/media/mc/mc-device.c:521:16:  warning: incorrect type in argument 1 (different address spaces)

Fixes: f4930887 ("media: media_device_enum_links32: clean a reserved field")
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/mc/mc-device.c

@@ -518,8 +518,9 @@ static long media_device_enum_links32(struct media_device *mdev,
 	if (ret)
 		return ret;
 
-	memset(ulinks->reserved, 0, sizeof(ulinks->reserved));
-
+	if (copy_to_user(ulinks->reserved, links.reserved,
+			 sizeof(ulinks->reserved)))
+		return -EFAULT;
 	return 0;
 }