speakup: Fix spurious space pronunciation on spelling letters

This gathers emitting the caps start string, space, spelled letter
string, space, and caps stop string, into one printf, to avoid
sending to the synth a space character alone, which the synth would
then pronounce.

Similarly, emit space along control-letter and letter spelling.

Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Tested-by: Zahari Yurukov <zahari.yurukov@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>