After recording PEBS-via-PT, perf script will not accept 'iregs' field e.g.

 # perf record -c 10000 -e '{intel_pt/branch=0/,branch-loads/aux-output/ppp}' -I -- ls -l
 ...
 [ perf record: Woken up 1 times to write data ]
 [ perf record: Captured and wrote 0.062 MB perf.data ]
 # ./perf script --itrace=eop -F+iregs
 Samples for 'dummy:u' event do not have IREGS attribute set. Cannot print 'iregs' field.

Fix by using allow_user_set, which is true when recording AUX area data.

Fixes: 9e64cefe ("perf intel-pt: Process options for PEBS event synthesis")
Signed-off-by: NAdrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Luwei Kang <luwei.kang@intel.com>
Link: http://lore.kernel.org/lkml/20200630133935.11150-3-adrian.hunter@intel.comSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>