staging: comedi: comedidev.h: spaces preferred around that '*'

Fix the checkpatch.pl issues:

CHECK: spaces preferred around that '*' (ctx:VxV)

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>