ASoC: twl6040: Fix TLV dB step values for gains

Some gains were incorrectly configured for dB values.
Signed-off-by: NMargarita Olaya Cabrera <magi.olaya@ti.com>
Acked-by: NMark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: NLiam Girdwood <lrg@slimlogic.co.uk>

sound/soc/codecs/twl6040.c

@@ -471,9 +471,9 @@ static DECLARE_TLV_DB_SCALE(mic_preamp_tlv, -600, 600, 0);
 
 /*
  * MICGAIN volume control:
- * from 6 to 30 dB in 6 dB steps
+ * from -6 to 30 dB in 6 dB steps
  */
-static DECLARE_TLV_DB_SCALE(mic_amp_tlv, 600, 600, 0);
+static DECLARE_TLV_DB_SCALE(mic_amp_tlv, -600, 600, 0);
 
 /*
  * AFMGAIN volume control: