Opaque parameters were previously added to the original definition of
ff_nv12ToUV, leading to gcc noticing a type mismatch with -Wlto-type-mismatch.

https://git.ffmpeg.org/gitweb/ffmpeg.git/commit/f2de911818fbd7e73343803626b697fd0c968121
https://bugs.gentoo.org/907484Signed-off-by: Alfred Wingate <parona@protonmail.com>
Signed-off-by: Anton Khirnov <anton@khirnov.net>