dix: Guard against non-existing PtrFeedbackPtr

Trying to change the pointer control settings on a device without
PtrFeedbackPtr would be a bug and a crash in the Xserver.

Guard against that case by returning early with a BadImplementation
error, that might kill the X11 client but the Xserver would survive.

Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>
Related: xorg/xserver#1137
(cherry picked from commit dee2bb03)
3 jobs for issue1137-1.20-branch in 7 minutes and 43 seconds (queued for 1 second)
Status Name Job ID Coverage
  Docker Image
passed debian-testing #10575928

00:00:25

 
  Build And Test
passed autotools-build-and-test #10575929

00:07:17

passed meson-build-and-test #10575930

00:02:33