speakup: Avoid crash on very long word

commit c8d2f34e upstream.

In case a console is set up really large and contains a really long word
(> 256 characters), we have to stop before the length of the word buffer.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Fixes: c6e3fd22 ("Staging: add speakup to the staging directory")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240323164843.1426997-1-samuel.thibault@ens-lyon.org


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