ASoC: ssm4567: Reset device before regcache_sync()

When the ssm4567 is powered up the driver calles regcache_sync() to restore
the register map content. regcache_sync() assumes that the device is in its
power-on reset state. Make sure that this is the case by explicitly
resetting the ssm4567 register map before calling regcache_sync() otherwise
we might end up with a incorrect register map which leads to undefined
behaviour.

One such undefined behaviour was observed when returning from system
suspend while a playback stream is active, in that case the ssm4567 was
kept muted after resume.

Fixes: 1ee44ce03011 ("ASoC: ssm4567: Add driver for Analog Devices SSM4567 amplifier")
Reported-by: Harsha Priya <[e-mail]>
Tested-by: Fang, Yang A <[e-mail]>
Signed-off-by: Lars-Peter Clausen <[e-mail]>
Signed-off-by: Mark Brown <[e-mail]>

sound/soc/codecs/ssm4567.c

···
 	regcache_cache_only(ssm4567->regmap, !enable);
 
 	if (enable) {
+		ret = regmap_write(ssm4567->regmap, SSM4567_REG_SOFT_RESET,
+			0x00);
+		if (ret)
+			return ret;
+
 		ret = regmap_update_bits(ssm4567->regmap,
 			SSM4567_REG_POWER_CTRL,
 			SSM4567_POWER_SPWDN, 0x00);