ASoC: fsl_ssi: Remove unneeded 'i2s-slave' property

There is no need to use 'i2s-slave' property, since master/slave configuration
are passed via machine layer.

This change does not break existing users because they do check for slave
mode inside sound/soc/fsl/mpc8610_hpcd.c/p1022_ds.c/p1022_rdk.c

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Timur Tabi <timur@tabi.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/fsl/fsl_ssi.c

@@ -1314,9 +1314,6 @@ static int fsl_ssi_probe(struct platform_device *pdev)
 	if (sprop) {
 		if (!strcmp(sprop, "ac97-slave"))
 			ssi_private->dai_fmt = SND_SOC_DAIFMT_AC97;
-		else if (!strcmp(sprop, "i2s-slave"))
-			ssi_private->dai_fmt = SND_SOC_DAIFMT_I2S |
-				SND_SOC_DAIFMT_CBM_CFM;
 	}
 
 	ssi_private->use_dma = !of_property_read_bool(np,