soc: renesas: rcar-sysc: Add r8a774c0 support

Add support for the RZ/G2E (R8A774C0) SoC power areas to the
R-Car SYSC driver.

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