kconfig: qconf: fix support for the split view mode

At least on my tests (building against Qt5.13), it seems to
me that, since Kernel 3.14, the split view mode is broken.

Maybe it was not a top priority during the conversion time.

Anyway, this patch changes the logic in order to properly
support the split view mode and the single view mode.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>