ASoC: rt1019: make symbol 'rt1019_i2c_driver' static

The sparse tool complains as follows:

sound/soc/codecs/rt1019.c:927:19: warning:
 symbol 'rt1019_i2c_driver' was not declared. Should it be static?

This symbol is not used outside of rt1019.c, so this
commit marks it static.

Fixes: 7ec79d38 ("ASoC: rt1019: add rt1019 amplifier driver")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Wei Yongjun <weiyongjun1@huawei.com>
Link: https://lore.kernel.org/r/20210319094102.4185096-1-weiyongjun1@huawei.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/rt1019.c

@@ -924,7 +924,7 @@ static int rt1019_i2c_probe(struct i2c_client *i2c,
 		&soc_component_dev_rt1019, rt1019_dai, ARRAY_SIZE(rt1019_dai));
 }
 
-struct i2c_driver rt1019_i2c_driver = {
+static struct i2c_driver rt1019_i2c_driver = {
 	.driver = {
 		.name = "rt1019",
 		.of_match_table = of_match_ptr(rt1019_of_match),