clk: renesas: Add R8A7792 support

Renesas R-Car V2H (R8A7792) clocks are handled by R-Car gen2 clock driver.

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