kconfig: qconf: fix signal connection to invalid slots

If you right-click in the ConfigList window, you will see the following
messages in the console:

QObject::connect: No such slot QAction::setOn(bool) in scripts/kconfig/qconf.cc:888
QObject::connect:  (sender name:   'config')
QObject::connect: No such slot QAction::setOn(bool) in scripts/kconfig/qconf.cc:897
QObject::connect:  (sender name:   'config')
QObject::connect: No such slot QAction::setOn(bool) in scripts/kconfig/qconf.cc:906
QObject::connect:  (sender name:   'config')

Right, there is no such slot in QAction. I think this is a typo of
setChecked.

Due to this bug, when you toggled the menu "Option->Show Name/Range/Data"
the state of the context menu was not previously updated. Fix this.

Fixes: d5d973c3

 ("Port xconfig to Qt5 - Put back some of the old implementation(part 2)")
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>