drm/nouveau/timer/ga10[024]: initial support

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

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

@@ -2662,6 +2662,7 @@ nv170_chipset = {
 	.imem = nv50_instmem_new,
 	.mc = ga100_mc_new,
 	.pci = gp100_pci_new,
+	.timer = gk20a_timer_new,
 };
 
 static const struct nvkm_device_chip
@@ -2674,6 +2675,7 @@ nv172_chipset = {
 	.imem = nv50_instmem_new,
 	.mc = ga100_mc_new,
 	.pci = gp100_pci_new,
+	.timer = gk20a_timer_new,
 };
 
 static const struct nvkm_device_chip
@@ -2686,6 +2688,7 @@ nv174_chipset = {
 	.imem = nv50_instmem_new,
 	.mc = ga100_mc_new,
 	.pci = gp100_pci_new,
+	.timer = gk20a_timer_new,
 };
 
 static int