KVM: x86: Drop ____kvm_handle_fault_on_reboot()

Remove the variation of __kvm_handle_fault_on_reboot() that accepts a
post-fault cleanup instruction now that its sole user (VMREAD) uses
a different method for handling faults.

Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>