perf tools: Remove perf_tool from event_op2

perf tools: Remove perf_tool from event_op2

Now that we keep a perf_tool pointer inside perf_session, there's no
need to have a perf_tool argument in the event_op2 callback. Remove it.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20180913125450.21342-2-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>