clk: renesas: Add r8a774a1 CPG Core Clock Definitions

Add all RZ/G2M Clock Pulse Generator Core Clock Outputs, as listed in
Table 8.2b ("List of Clocks [RZ/G2M]") of the RZ/G2M Hardware User's
Manual.

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