drivers/lis2dh12: use ifdef instead of IS_USED
drivers/lis2dh12: use ifdef instead of IS_USED

Using IS_USED leads to undefined API references

OlegHahm/RIOT,kYc0o/RIOT,kYc0o/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,kYc0o/RIOT,jasonatran/RIOT,RIOT-OS/RIOT,kaspar030/RIOT,OlegHahm/RIOT,kaspar030/RIOT,OlegHahm/RIOT,RIOT-OS/RIOT,RIOT-OS/RIOT,ant9000/RIOT,OlegHahm/RIOT,miri64/RIOT,kYc0o/RIOT,ant9000/RIOT,jasonatran/RIOT,ant9000/RIOT,kYc0o/RIOT,miri64/RIOT,miri64/RIOT,ant9000/RIOT,miri64/RIOT,kaspar030/RIOT,RIOT-OS/RIOT,miri64/RIOT,kaspar030/RIOT,ant9000/RIOT,jasonatran/RIOT,jasonatran/RIOT,kaspar030/RIOT,OlegHahm/RIOT