ASoC: sun50i-codec-analog: Make line out routes stereo

This matches the hardware more accurately, and is necessary for
including the (stereo) line out mute switch in the DAPM graph.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Link: https://lore.kernel.org/r/20200726025334.59931-7-samuel@sholland.org
Signed-off-by: Mark Brown <broonie@kernel.org>