KVM: s390: cleanup struct kvm_s390_float_interrupt

"wq" is not used at all. "cpuflags" can be access directly via the vcpu,
just as "float_int" via vcpu->kvm.
While at it, reuse _set_cpuflag() to make the code look nicer.

Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20180108193747.10818-1-david@redhat.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>