Basic audio dmac register only supports busif from 0 to 3,
in order to use busif4 ~ busif7 extended audio dmac registers
need to be used.

Based on similar work from Jiada Wang in commit 7a516e49 ("arm64:
dts: renesas: use extended audio dmac register").
Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>