perf/core: Call LSM hook after copying perf_event_attr

It passes the attr struct to the security_perf_event_open() but it's
not initialized yet.

Fixes: da97e184

 ("perf_event: Add support for LSM and SELinux checks")
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20221220223140.4020470-1-namhyung@kernel.org