drm/nouveau/tmr/gv100: initial support

Appears to be compatible with GK20A.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nvkm/engine/device/base.c

@@ -2406,6 +2406,7 @@ nv140_chipset = {
 	.ibus = gm200_ibus_new,
 	.mc = gp100_mc_new,
 	.pci = gp100_pci_new,
+	.timer = gk20a_timer_new,
 	.top = gk104_top_new,
 };