ARM: dts: r8a7745: Add sound support

Define the generic r8a7745(RZ/G1E) part of the sound device node.

This patch is based on the r8a7794 sound work by Sergei Shtylyov.

Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>