s390/pai: fix raw data collection for PMU pai_ext

Commit 838d9bb6 ("perf: Use sample_flags for raw_data")
changed the way the raw data of an event is collected.
Adjust the PMU pai_ext to the new scheme.

Fixes: 838d9bb6 ("perf: Use sample_flags for raw_data")
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Acked-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>