KVM: s390: add 'pgm' member to kvm_vcpu_arch and helper function
Add a 'struct kvm_s390_pgm_info pgm' member to kvm_vcpu_arch. This
structure will be used if during instruction emulation in the context
of a vcpu exception data needs to be stored somewhere.
Also add a helper function kvm_s390_inject_prog_cond() which can inject
vcpu's last exception if needed.