ASoC: tlv320aic26: use DEVICE_ATTR_RW macro

Use DEVICE_ATTR_RW() helper instead of plain DEVICE_ATTR(),
which makes the code a bit shorter and easier to read.

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Message-Id: <20210524115131.46288-1-yuehaibing@huawei.com>
Signed-off-by: Mark Brown <broonie@sirena.org.uk>