ASoC: rsnd: explain extended Audio DMAC peri peri address

If SoC has extended Audio DMAC peri peri address,
DT needs to select it.
Otherwise, it can select normal Audio DMAC peri peri address.
Extended Audio DMAC peri peri address can use BUSIF4-7,
normal address can't.
Reported-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Mark Brown <broonie@kernel.org>

Documentation/devicetree/bindings/sound/renesas,rsnd.txt

@@ -283,6 +283,8 @@ Required properties:
 				  required register is
 				   SRU/ADG/SSI      if generation1
 				   SRU/ADG/SSIU/SSI/AUDIO-DMAC-periperi if generation2/generation3
+				   Select extended AUDIO-DMAC-periperi address if SoC has it,
+				   otherwise select normal AUDIO-DMAC-periperi address.
 - reg-names			: Should contain the register names.
 				   scu/adg/ssi	if generation1
 				   scu/adg/ssiu/ssi/audmapp if generation2/generation3