Change the printf format character from 'd' to 'u' for the
VM-instruction error in vmwrite_error().

Fixes: 6aa8b732 ("[PATCH] kvm: userspace interface")
Reported-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Jim Mattson <jmattson@google.com>
Message-Id: <20220510224035.1792952-2-jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>