staging: speakup: (coding style) Add spaces around operands (checkpatch checks)

Fix checkpatch check: CHECK: spaces preferred around that '-' (ctx:VxV)
Add spaces around operands to fix these warnings.

Signed-off-by: Christian Colic <colic.christian@gmail.com>
Reviewed-by: Luis de Bethencourt <luisbg@osg.samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>