build: fix 'make rpm'

Since commit ddf3bd32, 'make rpm' failed with:

RPM build errors:
    File not found: /home/remote/eblake/rpmbuild/BUILDROOT/libvirt-0.9.6-1.fc14.eblake1318366440.x86_64/usr/share/systemtap/tapset/libvirtd.stp

* libvirt.spec.in (with_dtrace): Match installed .stp files.

libvirt.spec.in

@@ -969,7 +969,8 @@ fi
 rm -f $RPM_BUILD_ROOT%{_sysconfdir}/sysctl.d/libvirtd
 %endif
 %if %{with_dtrace}
-%{_datadir}/systemtap/tapset/libvirtd.stp
+%{_datadir}/systemtap/tapset/libvirt_probes.stp
+%{_datadir}/systemtap/tapset/libvirt_functions.stp
 %endif
 %dir %attr(0700, root, root) %{_localstatedir}/log/libvirt/qemu/
 %dir %attr(0700, root, root) %{_localstatedir}/log/libvirt/lxc/