perf scripts python: exported-sql-viewer.py: Fix unexpanded 'Find' result

Using Python version 3.8.2 and PySide2 version 5.14.0, ctrl-F ('Find')
would not expand the tree to the result. Fix by using setExpanded().

Example:

  $ perf record -e intel_pt//u uname
  Linux
  [ perf record: Woken up 1 times to write data ]
  [ perf record: Captured and wrote 0.034 MB perf.data ]
  $ perf script --itrace=bep -s ~/libexec/perf-core/scripts/python/export-to-sqlite.py perf.data.db branches calls
  2020-06-26 15:32:14.928997 Creating database ...
  2020-06-26 15:32:14.933971 Writing records...
  2020-06-26 15:32:15.535251 Adding indexes
  2020-06-26 15:32:15.542993 Dropping unused tables
  2020-06-26 15:32:15.549716 Done
  $ python3 ~/libexec/perf-core/scripts/python/exported-sql-viewer.py perf.data.db

  Select: Reports -> Context-Sensitive Call Graph    or     Reports -> Call Tree
  Press: Ctrl-F
  Enter: main
  Press: Enter

Before: line showing 'main' does not display

After: tree is expanded to line showing 'main'

Fixes: ebd70c7dc2 ("perf scripts python: exported-sql-viewer.py: Add ability to find symbols in the call-graph")
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: stable@vger.kernel.org
Link: http://lore.kernel.org/lkml/20200629091955.17090-4-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/scripts/python/exported-sql-viewer.py

@@ -1050,6 +1050,7 @@ class TreeWindowBase(QMdiSubWindow):
 				child = self.model.index(row, 0, parent)
 				if child.internalPointer().dbid == dbid:
 					found = True
+					self.view.setExpanded(parent, True)
 					self.view.setCurrentIndex(child)
 					parent = child
 					break