ASoC: omap-mcbsp: Remove unused FRAME dma_op_mode

The frame dma_op_mode has never been used, and it is just creating
confusion for users/developers.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Jarkko Nikula <jarkko.nikula@bitmer.com>
Signed-off-by: Liam Girdwood <lrg@ti.com>

sound/soc/omap/mcbsp.c

@@ -754,7 +754,7 @@ THRESHOLD_PROP_BUILDER(max_tx_thres);
 THRESHOLD_PROP_BUILDER(max_rx_thres);
 
 static const char *dma_op_modes[] = {
-	"element", "threshold", "frame",
+	"element", "threshold",
 };
 
 static ssize_t dma_op_mode_show(struct device *dev,