drm/nouveau/drm/nouveau: Pass the proper arguments to nvif_object_map_handle()

This is obviously wrong in the current code. Make sure to record the
correct size of the arguments and pass the actual arguments to the
nvif_object_map_handle() function.

Suggested-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>