arm64: dts: broadcom: bcmbca: bcm6858: add TWD block

BCM6858 contains TWD block with timers, watchdog, and reset subblocks.
Describe it.

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
Link: https://lore.kernel.org/r/20221103110015.21761-1-zajec5@gmail.com


Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>