perf scripts python: export-to-postgresql.py: Fix DROP VIEW power_events_view

PostgreSQL can error if power_events_view is not dropped before its
dependent tables e.g.

  Exception: Query failed: ERROR:  cannot drop table mwait because other
  objects depend on it
  DETAIL:  view power_events_view depends on table mwait
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Fixes: aba44287 ("perf scripts python: export-to-postgresql.py: Export Intel PT power and ptwrite events")
Link: http://lkml.kernel.org/r/20190708055232.5032-2-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/scripts/python/export-to-postgresql.py

@@ -898,11 +898,11 @@ def trace_end():
 	if is_table_empty("ptwrite"):
 		drop("ptwrite")
 	if is_table_empty("mwait") and is_table_empty("pwre") and is_table_empty("exstop") and is_table_empty("pwrx"):
+		do_query(query, 'DROP VIEW power_events_view');
 		drop("mwait")
 		drop("pwre")
 		drop("exstop")
 		drop("pwrx")
-		do_query(query, 'DROP VIEW power_events_view');
 		if is_table_empty("cbr"):
 			drop("cbr")