power: reset: brcmstb: Use devm_register_sys_off_handler()

Function register_restart_handler() is deprecated. Using this new API
removes our need to keep and manage a struct notifier_block.

Signed-off-by: Andrew Davis <afd@ti.com>
Reviewed-by: Dhruva Gole <d-gole@ti.com>
Acked-by: Florian Fainelli <florian.fainelli@broadcom.com>
Link: https://lore.kernel.org/r/20240610142836.168603-4-afd@ti.com


Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>