watchdog: sunxi: fix activation of system reset

Commit f2147de3 ("watchdog: sunxi: support parameterized compatible
strings") introduced a regression in sunxi_wdt_start(), by which
the system reset function of the watchdog is not enabled upon
starting the watchdog. As a result, the system is not reset when the
watchdog expires. Fix it.

Fixes: f2147de3

 ("watchdog: sunxi: support parameterized compatible strings")
Signed-off-by: Francesco Lavra <francescolavra.fl@gmail.com>
Acked-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Cc: stable@vger.kernel.org