drm/nvc0/fifo: avoid touching missing subfifos

Signed-off-by: Ben Skeggs <[e-mail]>

drivers/gpu/drm/nouveau/nvc0_fifo.c

···
 	}
 
 	/* PSUBFIFO[n] */
-	for (i = 0; i < 3; i++) {
+	for (i = 0; i < priv->spoon_nr; i++) {
 		nv_mask(dev, 0x04013c + (i * 0x2000), 0x10000100, 0x00000000);
 		nv_wr32(dev, 0x040108 + (i * 0x2000), 0xffffffff); /* INTR */
 		nv_wr32(dev, 0x04010c + (i * 0x2000), 0xfffffeff); /* INTR_EN */