ARM: dts: r8a7791: Tidyup Audio-DMAC channel for DVC

Current	Audio-DMAC is assigned "rx" as Audio-DMAC0, "tx" as Audio-DMAC1.
Thus, DVC "tx" should be assigned as Audio-DMAC1, instead of Audio-DMAC0.

Because of this, current platform board (using SRC/DVC/SSI)
Playback/Capture both will use same Audio-DMAC0
(but it depends on audio data path).

First note is that this "rx" and "tx" are from each IP point,
it doesn't mean Playback/Capture.
Second note is that Audio DMAC assigned on DT is only for
Audio-DMAC, Audio-DMAC-peri-peri has no entry.

=> Audio-DMAC
-> Audio-DMAC-peri-peri
-- HW connection

Playback case

	[Mem] => [SRC]--[DVC] -> [SSI]--[Codec]
	      rx ~~~~~~~~~~~~
Capture

	[Mem] <= [DVC]--[SRC] <- [SSI]--[Codec]
	      tx ~~~~~~~~~~~~

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>