media: vidtv: simplify PSI write function

The function vidtv_psi_ts_psi_write_into() initializes the
ts_header fields several times, and receives a struct
as argument, instead of using a pointer to struct.

Cleanup the function, in order to reduce its stack usage
and to avoid initializing the ts_header multiple times.

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