KVM: nSVM: restore clobbered INT_CTL fields after clearing VINTR

Restore the INT_CTL value from the guest's VMCB once we've stopped using
it, so that virtual interrupts can be injected as requested by L1.
V_TPR is up-to-date however, and it can change if the guest writes to CR8,
so keep it.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>