drm/nouveau/pmu/gk104: check fuse to determine presence of PGOB

Not 100% confirmed, but seems to match from the few boards I've looked
at so far.
Signed-off-by: NBen Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nvkm/subdev/pmu/gk104.c

@@ -27,6 +27,7 @@
 #include "fuc/gf119.fuc4.h"
 
 #include <core/option.h>
+#include <subdev/fuse.h>
 #include <subdev/timer.h>
 
 static void
@@ -57,6 +58,9 @@ gk104_pmu_pgob(struct nvkm_pmu *pmu, bool enable)
 {
 	struct nvkm_device *device = pmu->subdev.device;
 
+	if (!(nvkm_fuse_read(device->fuse, 0x31c) & 0x00000001))
+		return;
+
 	nvkm_mask(device, 0x000200, 0x00001000, 0x00000000);
 	nvkm_rd32(device, 0x000200);
 	nvkm_mask(device, 0x000200, 0x08000000, 0x08000000);