drivers: watchdog: exar_wdt.c fix use after free

fix use after free by storing the result of PTR_ERR(n->pdev)
to a local variable before returning.

Signed-off-by: Manank Patel <pmanank200502@gmail.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20221013095258.1424967-1-pmanank200502@gmail.com


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