watchdog: starfive: Fix resource leak in probe error path

watchdog: starfive: Fix resource leak in probe error path

If pm_runtime_put_sync() fails after watchdog_register_device()
succeeds, the probe function jumps to err_exit without
unregistering the watchdog device. This leaves the watchdog
registered in the subsystem while the driver fails to load,
resulting in a resource leak.

Add a new error label err_unregister_wdt to properly unregister
the watchdog device.

Fixes: 8bc22a2f1bf0 ("watchdog: starfive: Check pm_runtime_enabled() before decrementing usage counter")
Signed-off-by: Haotian Zhang <vulab@iscas.ac.cn>
Reviewed-by: Wim Van Sebroeck <wim@linux-watchdog.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>