drm/vc4: Reset ->{x, y}_scaling[1] when dealing with uniplanar formats

This is needed to ensure ->is_unity is correct when the plane was
previously configured to output a multi-planar format with scaling
enabled, and is then being reconfigured to output a uniplanar format.

Fixes: fc04023f ("drm/vc4: Add support for YUV planes.")
Cc: <stable@vger.kernel.org>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20180724133601.32114-1-boris.brezillon@bootlin.com

drivers/gpu/drm/vc4/vc4_plane.c

@@ -320,6 +320,9 @@ static int vc4_plane_setup_clipping_and_scaling(struct drm_plane_state *state)
 			vc4_state->x_scaling[0] = VC4_SCALING_TPZ;
 		if (vc4_state->y_scaling[0] == VC4_SCALING_NONE)
 			vc4_state->y_scaling[0] = VC4_SCALING_TPZ;
+	} else {
+		vc4_state->x_scaling[1] = VC4_SCALING_NONE;
+		vc4_state->y_scaling[1] = VC4_SCALING_NONE;
 	}
 
 	vc4_state->is_unity = (vc4_state->x_scaling[0] == VC4_SCALING_NONE &&