s390x/kvm: avoid syscalls by syncing registers with kvm_run

s390x/kvm: avoid syscalls by syncing registers with kvm_run

We can avoid loads of syscalls when dropping to user space by storing the values
of more registers directly within kvm_run.

Support is added for:
- ARCH0: CPU timer, clock comparator, TOD programmable register,
         guest breaking-event register, program parameter
- PFAULT: pfault parameters (token, select, compare)

Signed-off-by: David Hildenbrand <[email protected]>
Signed-off-by: Jens Freimann <[email protected]>
Reviewed-by: Cornelia Huck <[email protected]>
Acked-by: Christian Borntraeger <[email protected]>
Signed-off-by: Cornelia Huck <[email protected]>