KVM: s390: rename private structures

While doing some tests with our lcrash implementation I have seen a
naming conflict with prefix_info in kvm_host.h vs. addrconf.h

To avoid future conflicts lets rename private definitions in
asm/kvm_host.h by adding the kvm_s390 prefix.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>