clk: renesas: cpg-mssr: Add R8A7745 support

Add RZ/G1E (R8A7745) Clock Pulse Generator / Module Standby and Software
Reset support, using the CPG/MSSR driver core and the common R-Car Gen2
(and RZ/G) code.

Based on the proof-of-concept R8A7791 CPG/MSSR patch by Geert
Uytterhoeven <geert+renesas@glider.be>.

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>