Add sound support for the RZ/G2E SoC (a.k.a. R8A774C0).

This work is based on similar work done on the R8A77990 SoC
by Yoshihiro Kaneko <ykaneko0929@gmail.com>.
Signed-off-by: Fabrizio Castro <fabrizio.castro@bp.renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>