drm/radeon/kms: fix num_banks tiling config for fusion

The field is encoded:
0 = 4 banks
1 = 8 banks
2 = 16 banks
Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/evergreen.c

@@ -2013,9 +2013,9 @@ static void evergreen_gpu_init(struct radeon_device *rdev)
 		rdev->config.evergreen.tile_config |= (3 << 0);
 		break;
 	}
-	/* num banks is 8 on all fusion asics */
+	/* num banks is 8 on all fusion asics. 0 = 4, 1 = 8, 2 = 16 */
 	if (rdev->flags & RADEON_IS_IGP)
-		rdev->config.evergreen.tile_config |= 8 << 4;
+		rdev->config.evergreen.tile_config |= 1 << 4;
 	else
 		rdev->config.evergreen.tile_config |=
 			((mc_arb_ramcfg & NOOFBANK_MASK) >> NOOFBANK_SHIFT) << 4;