media: pci: cx18-av-vbi: Replace one-element array with flexible-array member

One-element arrays are deprecated, and we are replacing them with flexible
array members instead. So, replace one-element arrays with flexible-array
members in struct vbi_anc_data.

This results in no differences in binary output.

Link: https://github.com/KSPP/linux/issues/79



Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>