dt-bindings: watchdog: renesas,wdt: Add support for RZ/T2H and RZ/N2H

dt-bindings: watchdog: renesas,wdt: Add support for RZ/T2H and RZ/N2H

Extend the Renesas WDT device tree bindings to support the watchdog timer
found on the RZ/T2H (R9A09G077) and RZ/N2H (R9A09G087) SoCs.

The RZ/T2H WDT is mostly compatible with the one found on the RZ/V2H(P),
but includes an additional register and differs in the clock division
ratio settings for the WDTCR[CKS] field. To reflect these differences,
introduce a new compatible string, "renesas,r9a09g077-wdt".

The binding schema is updated accordingly. On RZ/T2H, the WDT does not
require the "resets" property. It also requires two register regions and
the presence of a "power-domains" property. The "clock-names" property is
limited to a single entry, "pclk", for this SoC.

The RZ/N2H SoC uses the same WDT IP as the RZ/T2H. It is supported by
using "renesas,r9a09g087-wdt" as the primary compatible string, with
"renesas,r9a09g077-wdt" listed as a fallback to describe the shared
hardware features.

Example:
    wdt0: watchdog@80082000 {
        compatible = "renesas,r9a09g077-wdt";
        reg = <0 0x80082000 0 0x400>,
              <0 0x81295100 0 0x04>;
        clocks = <&cpg CPG_CORE R9A09G077_CLK_PCLKL>;
        clock-names = "pclk";
        power-domains = <&cpg>;
        status = "disabled";
    };

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Rob Herring (Arm) <robh@kernel.org>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>