media: v4l2-ctrl: Initialize _BUTTON and _CTRL_CLASS

These two control types don't really need a default value,
as they are not expected to carry any value.

However, it's slightly clearer to initialize them explicitly
instead of falling back to the switch default.
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/media/v4l2-core/v4l2-ctrls.c

@@ -1520,6 +1520,10 @@ static void std_init(const struct v4l2_ctrl *ctrl, u32 idx,
 	case V4L2_CTRL_TYPE_BOOLEAN:
 		ptr.p_s32[idx] = ctrl->default_value;
 		break;
+	case V4L2_CTRL_TYPE_BUTTON:
+	case V4L2_CTRL_TYPE_CTRL_CLASS:
+		ptr.p_s32[idx] = 0;
+		break;
 	case V4L2_CTRL_TYPE_U8:
 		ptr.p_u8[idx] = ctrl->default_value;
 		break;