ASoC: McASP: Convert driver to use Runtime PM API

* Add Runtime PM support to McASP host controller.
  * Use Runtime PM API to enable/disable McASP clock.

This was tested on AM18x Board using suspend/resume

Signed-off-by: Hebbar, Gururaja <gururaja.hebbar@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/davinci/davinci-mcasp.h

@@ -40,9 +40,8 @@ struct davinci_audio_dev {
 	struct davinci_pcm_dma_params dma_params[2];
 	void __iomem *base;
 	int sample_rate;
-	struct clk *clk;
+	struct device *dev;
 	unsigned int codec_fmt;
-	u8 clk_active;
 
 	/* McASP specific data */
 	int	tdm_slots;