ASoC: fsl_spdif: Add core clock control for DMA access

ASoC: fsl_spdif: Add core clock control for DMA access

Regmap is able to enable/disable the core clock automatically each time
it's going to access the registers. But for DMA cases during playback or
recording, it's totally beyong control of regmap. So we have to open the
clock manually.

Signed-off-by: Nicolin Chen <Guangyu.Chen@freescale.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
(cherry picked from commit 08f7336e6404698158966d0c8a2937d3580e2693)