speakup_soft: Add direct module parameter

For non-english speech synthesis, it is often desirable to make
speakup_soft pass text directly.  Adding a direct parameter to the
speakup_soft module allows to easily set that at boot, rather than
setting the sys variable after boot.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Link: https://lore.kernel.org/r/20220829203625.6s6x57miowu4p664@begin
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>