drm/nv50-/sw: make vblank tracking data private to the implementations

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

diff --cc drivers/gpu/drm/nouveau/core/engine/software/nv50.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/engine/software/nv50.h
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/engine/software/nvc0.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/core/include/engine/software.h
Simple merge