The VP8_FRAME_HEADER control type is validated, so it
needs a corresponding initialization to produce default
legal values.

For now, only add the minimum required initialization
to satisfy current validation.
Signed-off-by: NEzequiel Garcia <ezequiel@collabora.com>
Signed-off-by: NHans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: NMauro Carvalho Chehab <mchehab+huawei@kernel.org>