power/reset: Remove sun6i reboot driver

sun6i restart is now handled by its watchdog driver directly,
so this driver is no longer needed.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>