drm/nouveau/disp: expose page flip event class

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>

drm/nouveau/nvif: split out nvsw interface definitons

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drm/nouveau/sw: convert to new-style nvkm_engine

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drm/nouveau/sw: convert user classes to new-style nvkm_object

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drm/nouveau/sw: turn flip completion into an event

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>