watchdog: imx7ulp: Fix reboot hang

The following hang is observed when a 'reboot' command is issued:

# reboot
# Stopping network: OK
Stopping klogd: OK
Stopping syslogd: OK
umount: devtmpfs busy - remounted read-only
[    8.612079] EXT4-fs (mmcblk0p2): re-mounted. Opts: (null)
The system is going down NOW!
Sent SIGTERM to all processes
Sent SIGKILL to all processes
Requesting system reboot
[   10.694753] reboot: Restarting system
[   11.699008] Reboot failed -- System halted

Fix this problem by adding a .restart ops member.

Fixes: 41b630f4 ("watchdog: Add i.MX7ULP watchdog support")
Signed-off-by: Fabio Estevam <festevam@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20191029174037.25381-1-festevam@gmail.com


Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>