Register with kernel restart handler instead of setting arm_pm_restart directly.

Move notifier registration to the end of the probe function to avoid having to
implement error handling.

Cc: Ivan Khoronzhuk <ivan.khoronzhuk@ti.com>
Cc: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: NSantosh Shilimkar <santosh.shilimkar@ti.com>
Tested-by: NIvan Khoronzhuk <ivan.khoronzhuk@ti.com>
Signed-off-by: NGuenter Roeck <linux@roeck-us.net>

The keystone SoC can be rebooted in several ways. By external reset
pin, by soft and by watchdogs. To allow keystone SoC reset if
watchdog is triggered we have to enable it in reset mux configuration
register regarding of watchdog configuration. Also we need to set
soft/hard reset we are going to use.

So add keystone reset driver to handle all this stuff.
Reviewed-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NIvan Khoronzhuk <ivan.khoronzhuk@ti.com>
Signed-off-by: NSantosh Shilimkar <santosh.shilimkar@ti.com>