drm/nvd0/disp: mask off high 16 bit of negative cursor x-coordinate

commit af5e7d84b0ec45b2b614b0d6e3657cbdceaa21f9 upstream.

Signed-off-by: Christoph Bumiller <e0425955@student.tuwien.ac.at>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
[bwh: Backported to 3.2: register value is in the local 'data' variable]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --cc drivers/gpu/drm/nouveau/nvd0_display.c
Simple merge