perf tools: Remove static debugfs path from parse-events

Timechart doesn't work if debugfs is not in /sys/kernel/debug/.
Fixed by using global debugfs_path which is filled in by perf.

Signed-off-by: Ashwin Chaugule <ashwinc@quicinc.com>
Cc: "Arjan van de Ven" <arjan@linux.intel.com>
LKML-Reference: <a751bdc6978478de6d10440e587a2cc7.squirrel@www.codeaurora.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>