watchdog: diag288_wdt: de-duplicate diag_stat_inc() calls

Call diag_stat_inc() from __diag288() to reduce code duplication.

Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Link: https://lore.kernel.org/r/20230203073958.1585738-5-egorenar@linux.ibm.com


Signed-off-by: Heiko Carstens <hca@linux.ibm.com>