drm/nouveau/gr/gm200: modify the mask when copying mmu settings from fb

Appears to more closely match what RM does.

For GM20B, now also copying bit 12 from NV_PFB_MMU_CTRL as upcoming
changes will require it.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nvkm/engine/gr/gm200.c

@@ -36,10 +36,8 @@ static void
 gm200_gr_init_gpc_mmu(struct gf100_gr *gr)
 {
 	struct nvkm_device *device = gr->base.engine.subdev.device;
-	u32 tmp;
 
-	tmp = nvkm_rd32(device, 0x100c80); /*XXX: mask? */
-	nvkm_wr32(device, 0x418880, 0x00001000 | (tmp & 0x00000fff));
+	nvkm_wr32(device, 0x418880, nvkm_rd32(device, 0x100c80) & 0xf0001fff);
 	nvkm_wr32(device, 0x418890, 0x00000000);
 	nvkm_wr32(device, 0x418894, 0x00000000);
 

drivers/gpu/drm/nouveau/nvkm/engine/gr/gm20b.c

@@ -42,7 +42,7 @@ gm20b_gr_init_gpc_mmu(struct gf100_gr *gr)
 	}
 
 	val = nvkm_rd32(device, 0x100c80);
-	val &= 0xf000087f;
+	val &= 0xf000187f;
 	nvkm_wr32(device, 0x418880, val);
 	nvkm_wr32(device, 0x418890, 0);
 	nvkm_wr32(device, 0x418894, 0);