ASoC: fsl: remove helper fsl_asoc_get_codec_dev_name

The ASoC core now can support matching codec with device node besides
name, so we can save helper function fsl_asoc_get_codec_dev_name.

Signed-off-by: Shawn Guo <shawn.guo@linaro.org>
Acked-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Timur Tabi <timur@freescale.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>