Always initialize SDL with the video subsystem

Clipboard synchronization requires SDL_INIT_VIDEO, so always initialize
the video subsystem, even if --no-video or --no-video-playback is
passed.

Refs caf594c90ef1b71ed844b2a9b42c3b3371215d6f
Fixes #4418 <https://github.com/Genymobile/scrcpy/issues/4418>