s390/qdio: adopt new tasklet API

Convert the Output Queue tasklet code to take a tasklet_struct as
parameter. Then initialize the tasklet with tasklet_setup() to indicate
that we follow the new model.

Signed-off-by: Julian Wiedmann <jwi@linux.ibm.com>
Reviewed-by: Benjamin Block <bblock@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>