perf timechart: Remove open-coded event parsing code

Convert builtin-timechart.c to mmap_dispatch_perf_file() +
perf_file_handler.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Arjan van de Ven <arjan@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <4B14B21C.2040406@cn.fujitsu.com>
[ v2: cleaned up the printout, fixed a whitespace detail ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>