drm/vc4: Add support for NV21 and NV61.

NV12 (YUV420 2 plane) and NV16 (YUV422 2 plane) were
supported, but NV21 and NV61 (same but with Cb and Cr
swapped) weren't. Add them.
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>
Signed-off-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/1f50799525e3401551dff2b0b2828b9ab892f75f.1510841336.git.dave.stevenson@raspberrypi.org

drivers/gpu/drm/vc4/vc4_plane.c

@@ -152,11 +152,21 @@ static const struct hvs_format {
 		.hvs = HVS_PIXEL_FORMAT_YCBCR_YUV420_2PLANE,
 		.pixel_order = HVS_PIXEL_ORDER_XYCBCR,
 	},
+	{
+		.drm = DRM_FORMAT_NV21,
+		.hvs = HVS_PIXEL_FORMAT_YCBCR_YUV420_2PLANE,
+		.pixel_order = HVS_PIXEL_ORDER_XYCRCB,
+	},
 	{
 		.drm = DRM_FORMAT_NV16,
 		.hvs = HVS_PIXEL_FORMAT_YCBCR_YUV422_2PLANE,
 		.pixel_order = HVS_PIXEL_ORDER_XYCBCR,
 	},
+	{
+		.drm = DRM_FORMAT_NV61,
+		.hvs = HVS_PIXEL_FORMAT_YCBCR_YUV422_2PLANE,
+		.pixel_order = HVS_PIXEL_ORDER_XYCRCB,
+	},
 };
 
 static const struct hvs_format *vc4_get_hvs_format(u32 drm_format)