media: v4l2-ioctl.c: zero reserved fields for S/TRY_FMT

commit ee8951e56c0f960b9621636603a822811cef3158 upstream.

v4l2_vbi_format, v4l2_sliced_vbi_format and v4l2_sdr_format
have a reserved array at the end that should be zeroed by drivers
as per the V4L2 spec. Older drivers often do not do this, so just
handle this in the core.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>