clk: renesas: cpg-mssr: Add r8a774b1 support

Add RZ/G2N (R8A774B1) Clock Pulse Generator / Module Standby and Software
Reset support.

Based on the Table 8.4d of "RZ/G Series, 2nd Generation User's Manual:
Hardware (Rev. 0.80, May 2019)".

Signed-off-by: Biju Das <biju.das@bp.renesas.com>
Link: https://lore.kernel.org/r/1568881036-4404-7-git-send-email-biju.das@bp.renesas.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>