ASoC: max98088: add support for noise gate reg

Add support for Noise Gate Threshold reg (ANTH reg 0x40 bit 4 to 7)

References:
 - https://datasheets.maximintegrated.com/en/ds/MAX98089.pdf, p75
Signed-off-by: Tommaso Merciai <tommaso.merciai@amarulasolutions.com>
Link: https://lore.kernel.org/r/20220825101714.81580-1-tommaso.merciai@amarulasolutions.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/max98088.c

@@ -474,6 +474,9 @@ static const struct snd_kcontrol_new max98088_snd_controls[] = {
                        max98088_mic2pre_get, max98088_mic2pre_set,
                        max98088_micboost_tlv),
 
+        SOC_SINGLE("Noise Gate Threshold", M98088_REG_40_MICAGC_THRESH,
+               4, 15, 0),
+
        SOC_SINGLE("INA Volume", M98088_REG_37_LVL_INA, 0, 7, 1),
        SOC_SINGLE("INB Volume", M98088_REG_38_LVL_INB, 0, 7, 1),