drm/nouveau: use drm_mm in preference to custom code doing the same thing

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

diff --cc drivers/gpu/drm/nouveau/nouveau_drv.h
Simple merge

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

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

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

diff --cc drivers/gpu/drm/nouveau/nv04_instmem.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/nv50_display.c
Simple merge

diff --cc drivers/gpu/drm/nouveau/nv50_instmem.c
Simple merge