ASoC: rsnd: tidyup rsnd_get_slot_xxx() naming

rsnd_get_slot_rdai() returns total slots (it returns 6 if total 6
channels) , and rsnd_get_slot_extend() returns extended SSI width
(it returns 8 if total 6 channels). This will be used on SSI multi
channel support too (It will return 2 if total 6 channels with 3 SSI).
But, it is using confusable naming.
This patch changes rsnd_get_slot_rdai() -> rsnd_get_slot(),
rsnd_get_slot_extend() -> rsnd_get_slot_width()

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/sound/soc/sh/rcar/ssiu.c b/sound/soc/sh/rcar/ssiu.c
index c7f89be..7ae05a7 100644
--- a/sound/soc/sh/rcar/ssiu.c
+++ b/sound/soc/sh/rcar/ssiu.c
@@ -78,7 +78,7 @@
 	if (ret < 0)
 		return ret;
 
-	if (rsnd_get_slot_extend(io) >= 6) {
+	if (rsnd_get_slot_width(io) >= 6) {
 		/*
 		 * TDM Extend Mode
 		 * see