arm64: dts: renesas: r8a77965: add SSIU support for sound

rsnd driver supports SSIU now, let's use it.
Then, BUSIF DMA settings on rcar_sound,ssi (= rxu, txu) are
no longer needed.
Applies commit 8d14bfa0 ("arm64: dts: renesas: r8a7796: add SSIU
support for sound") and commit 10bd03fa ("arm64: dts: renesas:
r8a7796: remove BUSIF0 settings from rcar_sound,ssi") for r8a77965.

Signed-off-by: Jiada Wang <jiada_wang@mentor.com>
Signed-off-by: Timo Wischer <twischer@de.adit-jv.com>
Acked-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>