Staging: comedi: Undo stupid commit made 3 months ago

Undo stupid commit made 3 months ago :
 "Fix redefinition of macro comedi_rt_task_context_t".
 It wasn't being redefined, it was being defined for RTLinux.

From: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Frank Mori Hess <fmhess@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>