clk: renesas: r8a7796: Add R8A77961 CPG/MSSR support

clk: renesas: r8a7796: Add R8A77961 CPG/MSSR support

Add support for the R-Car M3-W+ (R8A77961) SoC to the Renesas Clock
Pulse Generator / Module Standby and Software Reset driver.

R-Car M3-W+ is very similar to R-Car M3-W (R8A77960), which allows for
both SoCs to share a driver.  R-Car M3-W+ lacks a few modules, so their
clocks must be nullified.

Based on a patch in the BSP by Takeshi Kihara
<takeshi.kihara.df@renesas.com>.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Tested-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Link: https://lore.kernel.org/r/20191023122941.12342-5-geert+renesas@glider.be