ASoC: rt715: add vendor clear control register

Add vendor clear control register in readable register's
callback function. This prevents an access failure reported
in Intel CI tests.

Signed-off-by: Jack Yu <jack.yu@realtek.com>
Closes: thesofproject#4860
Tested-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/6a103ce9134d49d8b3941172c87a7bd4@realtek.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: Jack Yu

sound/soc/codecs/rt715-sdw.c

@@ -111,6 +111,7 @@ static bool rt715_readable_register(struct device *dev, unsigned int reg)
 	case 0x839d:
 	case 0x83a7:
 	case 0x83a9:
+	case 0x752001:
 	case 0x752039:
 		return true;
 	default: