watchdog: imx_sc_wdt: fix pretimeout

If the WDIOF_PRETIMEOUT flag is not set when registering the device the
driver will not show the sysfs entries or register the default governor.
By moving the registering after the decision whether pretimeout is
supported this gets fixed.

Signed-off-by: Stefan Eichenberger <eichest@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
Link: https://lore.kernel.org/r/20210519080311.142928-1-eichest@gmail.com
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>