When bootgraph.pl parses a file, it gives one row
for each initcall's pid. But only few of them will
be displayed => the longest.

This patch corrects it by giving only a rows for pids
which have initcalls that will be displayed.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Acked-by: NArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>