ASoC: tlv320aic32x4: Add additional input pins

The input mixers support routing the IN1_R pin to the Left PGA and the
IN2_L pin to the Right PGA.  This patch allows for those routings.

Signed-off-by: Jeremy McDermond <nh6z@nh6z.net>
Signed-off-by: Mark Brown <broonie@kernel.org>