watchdog: clean return of installkernel()

return 0, otherwise if _alldrivers is empty, the return code is fail

modules.d/04watchdog/module-setup.sh

@@ -73,4 +73,6 @@ installkernel() {
     # ensure that watchdog module is loaded as early as possible
     _alldrivers="${!_drivers[*]}"
     [[ $_alldrivers ]] && echo "rd.driver.pre=${_alldrivers// /,}" > ${initdir}/etc/cmdline.d/00-watchdog.conf
+
+    return 0
 }