perf timechart: Fix black idle boxes in the title

This fix is needed for eye of gnome and firefox svg viewers.
Only Inkscape can handle the broken case.

Compare with the other svg_legenda_box declarations, looks
like a typo slipped in at this place.

Signed-off-by: Thomas Renninger <trenn@suse.de>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: lenb@kernel.org
LKML-Reference: <1298842606-55712-5-git-send-email-trenn@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>