clk: renesas: Add r8a7743 CPG Core Clock Definitions

Add macros usable by the device tree sources to reference the R8A7743 CPG
clocks by index. The data comes from Table 7.2b in revision 1.00 of the
RZ/G Series User's Manual.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>