davinci-mcasp: fix _CBM_CFS pin directions

The current davinci_mcasp_set_dai_fmt() sets bits ACLKX and ACLKR in the PDIR
register for the codec clock-master/frame-slave mode; however, this results in
the ACLKX and ACLKR pins being outputs according to SPRUFM1 [1]  which
conflicts with "codec is clock master."

Similarly to the previous patch in this series, "fix _CBM_CFS hw_params" --
For codec clock-master/frame-slave mode (_CMB_CFS), clear bits ACLKX and ACLKR
in the PDIR register to set the pins as inputs and hence allow externally
sourced bit-clocks.

[1] http://www.ti.com/litv/pdf/sprufm1

Signed-off-by: Ben Gardiner <bengardiner@nanometrics.ca>
Reviewed-by: James Nuss <jamesnuss@nanometrics.ca>
Acked-by: Liam Girdwood <lrg@ti.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/davinci/davinci-mcasp.c

@@ -445,8 +445,10 @@ static int davinci_mcasp_set_dai_fmt(struct snd_soc_dai *cpu_dai,
 		mcasp_clr_bits(base + DAVINCI_MCASP_ACLKRCTL_REG, ACLKRE);
 		mcasp_set_bits(base + DAVINCI_MCASP_RXFMCTL_REG, AFSRE);
 
+		mcasp_clr_bits(base + DAVINCI_MCASP_PDIR_REG,
+				ACLKX | ACLKR);
 		mcasp_set_bits(base + DAVINCI_MCASP_PDIR_REG,
-				ACLKX | AFSX | ACLKR | AFSR);
+				AFSX | AFSR);
 		break;
 	case SND_SOC_DAIFMT_CBM_CFM:
 		/* codec is clock and frame master */