perf evsel: Force sample_type for slave events

Force sample_type setup for slave events in group leader sessions.

We don't get sample for slave events, we make them when delivering group
leader sample. Set the slave event to follow the master sample_type to
ease up report.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20190220122800.864-3-jolsa@kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>