clk: renesas: Add r8a7744 CPG Core Clock Definitions

Add all RZ/G1N Clock Pulse Generator Core Clock Outputs, as listed in
Table 7.2b ("List of Clocks [RZ/G1M/N]") of the RZ/G1 Hardware User's
Manual.

Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Reviewed-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>