dt-bindings: clock: Add r8a77961 CPG Core Clock Definitions

Add all Clock Pulse Generator Core Clock Outputs for the Renesas R-Car
M3-W+ (R8A77961) SoC, as listed in Table 8.2b ("List of Clocks [R-Car
M3-W/R-Car M3-W+]") of the R-Car Series, 3rd Generation Hardware User's
Manual (Rev. 2.00, Jul. 31, 2019).  A gap is added for CSIREF, to
preserve compatibility with the definitions for R-Car M3-W (R8A77960).

Note that internal CPG clocks (S0, S1, S2, S3, SDSRC, SSPSRC, and POST2)
are not included, as they are used as internal clock sources only, and
never referenced from DT.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20191023122941.12342-3-geert+renesas@glider.be