watchdog: rzv2h: Add support for RZ/T2H

watchdog: rzv2h: Add support for RZ/T2H

Add support for the RZ/T2H watchdog timer. The RZ/T2H requires control of
the watchdog counter using the WDT Debug Control Register (WDTDCR), which
allows explicitly stopping and starting the counter. This behavior differs
from RZ/V2H, which doesn't have WDTDCR, so the driver is extended to handle
this requirement.

To support this, a new `wdtdcr` flag is introduced in the `rzv2h_of_data`
structure. When set, the driver maps the WDTDCR register and uses it to
control the watchdog counter in the start, stop, and restart callbacks.
Additionally, the clock divisor and count source for RZ/T2H are defined
to match its hardware configuration.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
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>