clk: renesas: cpg-mssr: Add R8A77995 support

Add R-Car D3 (R8A77995) Clock Pulse Generator / Module Standby and
Software Reset support, using the CPG/MSSR driver core and the common
R-Car Gen3 CPG code.

Based on the R-Car Series, 3rd Generation Hardware User's Manual, Rev.
0.55, Jun. 30, 2017.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>
Acked-by: Rob Herring <robh@kernel.org>