perf scripts python: export-to-postgresql.py: Export calls parent_id

Export to the 'calls' table the newly created 'parent_id' and create an
index for it.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: https://lkml.kernel.org/n/tip-eybd6fnk6j9r7g643lsideoo@git.kernel.org


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