ARM: 9093/1: drivers: firmwapsci: Register with kernel restart handler

Register with kernel restart handler instead of setting arm_pm_restart
directly. This enables support for replacing the PSCI restart handler
with a different handler if necessary for a specific board.

Select a priority of 129 to indicate a higher than default priority, but
keep it as low as possible since PSCI reset is known to fail on some
boards.

Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>