drm/nouveau: fix fetching vbios from above 4GiB vram addresses

Signed-off-by: NBen Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nouveau_bios.c

@@ -135,13 +135,14 @@ static void load_vbios_pramin(struct drm_device *dev, uint8_t *data)
 	int i;
 
 	if (dev_priv->card_type >= NV_50) {
-		uint32_t vbios_vram = (nv_rd32(dev, 0x619f04) & ~0xff) << 8;
-
-		if (!vbios_vram)
-			vbios_vram = (nv_rd32(dev, 0x1700) << 16) + 0xf0000;
+		u64 addr = (u64)(nv_rd32(dev, 0x619f04) & 0xffffff00) << 8;
+		if (!addr) {
+			addr  = (u64)nv_rd32(dev, 0x1700) << 16;
+			addr += 0xf0000;
+		}
 
 		old_bar0_pramin = nv_rd32(dev, 0x1700);
-		nv_wr32(dev, 0x1700, vbios_vram >> 16);
+		nv_wr32(dev, 0x1700, addr >> 16);
 	}
 
 	/* bail if no rom signature */