ASoC: atmel-ssc: distinguish whether SSC supports fslen ext

Add compatible string to distinguish whether SSC supports
frame sync length extension.

Signed-off-by: Bo Shen <voice.shen@atmel.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Mark Brown <broonie@linaro.org>
diff --git a/include/linux/atmel-ssc.h b/include/linux/atmel-ssc.h
index 571a12e..e8dd408 100644
--- a/include/linux/atmel-ssc.h
+++ b/include/linux/atmel-ssc.h
@@ -7,6 +7,7 @@
 
 struct atmel_ssc_platform_data {
 	int			use_dma;
+	int			has_fslen_ext;
 };
 
 struct ssc_device {