media: vidtv: rewrite the adaption field logic

When compared with a stream generated via ffmpeg, it can be
noticed that the PES doesn't contain any PCR info. That could
cause problems with userspace decoding. So, rewrite the
logic that fills the adaptation info, in order to allow it
to add PCR frames without breaking frame alignment.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>