segafilm: drop the "song and dance" for cinepak

This seems not to do anything any more since a long time, and removing
it avoids using uninitialized memory. Also change the error value
forwarding as done everywhere else.

Partly fixes: msan_uninit-mem_7fb7d24780d0_2744_R03T.CAK
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>
