Staging: speakup: Add identifier name to function declaration arguments.

void (*read_buff_add) argument didn't have an identifier name,
adding a name to it like the rest of all functions' arguments.

Signed-off-by: Sam Muhammed <jane.pnx9@gmail.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Link: https://lore.kernel.org/r/b2a1ca962553194840d8cd2bf1f7d3174e3b1336.1585046066.git.jane.pnx9@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>