staging: speakup: i18n.c: Refactor conditionals in spk_msg_set

Reduce the indentation level in spk_msg_set and remove
unnecessary return variable.

Signed-off-by: Narcisa Ana Maria Vasile <narcisaanamaria12@gmail.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>