staging: speakup: kobjects.c: Use correct values when changing voice.

When a new voice is selected, we set volume and pitch appropriate for
the voice.  We need to use the numeric index corresponding to the
voice when indexing into the volume and pitch tables, rather than
the raw user input that was used to select the voice.
Note that using the raw input can also lead to an invalid memory read
in the case of invalid or malicious user input.

Signed-off-by: Christopher Brannon <chris@the-brannons.com>
Acked-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>