ASoC: rcar: fixup generation checker

Current rcar is using rsnd_is_gen1/gen2() to checking its
IP generation, but it needs data mask.
This patch fixes it up.

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

include/sound/rcar_snd.h

@@ -68,6 +68,7 @@ struct rsnd_scu_platform_info {
  *
  * A : generation
  */
+#define RSND_GEN_MASK	(0xF << 0)
 #define RSND_GEN1	(1 << 0) /* fixme */
 #define RSND_GEN2	(2 << 0) /* fixme */