dt-bindings: watchdog: Add support for TI K3 RTI watchdog

TI K3 SoCs contain an RTI (Real Time Interrupt) module which can be
used to implement a windowed watchdog functionality. Windowed watchdog
will generate an error if it is petted outside the time window, either
too early or too late.

Cc: Rob Herring <robh@kernel.org>
Cc: devicetree@vger.kernel.org
Signed-off-by: Tero Kristo <t-kristo@ti.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200312095808.19907-2-t-kristo@ti.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>