selftests/kvm: remove dead file

This file was supposed to be removed in commit 2b7deea ("Revert
"kvm: selftests: move base kvm_util.h declarations to kvm_util_base.h""),
but it survived.  Remove it now.

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

Author: bonzini