clk: renesas: Add r8a7794 CPG Core Clock Definitions

Add all R-Car E2 Clock Pulse Generator Core Clock Outputs, as listed in
Table 7.2d ("List of Clocks [R-Car E2]") of the R-Car Gen2 Hardware
User's Manual rev. 2.00.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>