ASoC: rsnd: add TDM Extend Mode support

Renesas R-Car can out TDM by
1) 6ch x 1 DAI as TDM Extend Mode
2) 2ch x 4 x 1 DAI as TDM split Mode
3) 2ch x 3 DAI or
   2ch x 4 DAI as TDM Multichannel Mode

This patch adds 1) TDM Extend Mode. Because of HW design,
this 6ch data will be outputed via 8ch data width.

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sh/rcar/rsnd.h

@@ -44,6 +44,7 @@
  */
 enum rsnd_reg {
 	/* SCU (SRC/SSIU/MIX/CTU/DVC) */
+	RSND_REG_SSI_MODE,		/* Gen2 only */
 	RSND_REG_SSI_MODE0,
 	RSND_REG_SSI_MODE1,
 	RSND_REG_SSI_CTRL,		/* Gen2 only */