Fix typo in 'self._channel' (thanks @akx)
Fix typo in 'self._channel' (thanks @akx)

caseyc37/pygame_cffi,GertBurger/pygame_cffi,caseyc37/pygame_cffi,GertBurger/pygame_cffi,CTPUG/pygame_cffi,CTPUG/pygame_cffi,GertBurger/pygame_cffi,caseyc37/pygame_cffi,GertBurger/pygame_cffi,CTPUG/pygame_cffi