The default implementation for setSelected() at QTreeWidgetItem
allows multiple items to be selected.

Well, this should never be possible for the configItem lists.

So, implement a function that will automatically clean any
previous selection. This simplifies the logic somewhat, while
making the selection logic to be applied atomically, avoiding
future issues on that.
Signed-off-by: NMauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: NMasahiro Yamada <masahiroy@kernel.org>