KVM: s390: remove the tasklet used by the hrtimer

We can get rid of the tasklet used for waking up a VCPU in the hrtimer
code but wakeup the VCPU directly.

Signed-off-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>